Interesting tidbits of info from the 156-page March 29, 1974 Second Revised Shooting Final screenplay:

Note - not all of this correlates with the movie

Description of the building: "The World's Tallest Skyscraper - majestic... awesome... gleaming gold - glittering panels covering structural steel - the whole pierced by tens of thousands of solar bronze-tinted tempered glass windows - the newest and most magnificent structure in the world."

The elevator going to the rooftop heliport is called the Executive Elevator.

On Duncan: "At fifty-three, one of the world's richest men, a tough-up-from-the-streets developer-builder. Even with his business suit pummeled by the wind, he gives off an aura of success and power. He appears - at the moment - to be literally and figuratively on top of the world - waiting up there alone for Craig [aka Doug] to buzz on down."

Will Giddings' role is "Construction Chief for Duncan Enterprises"

Callahan is the "Chief Engineer", and Wes is the "Assistant Engineer"

The security area is the 50th floor Central Security Center

The main area of 81 is the Residential Reception Area

Description of 79: "The [central room] area dominates the major part of this still-unrented floor currently given over to the planning work for all Duncan Enterprises' building projects"

In the first appearance of Lisolette Mueller, she's in Mueller Gallery in the building's lobby (or mezzanine - in the movie there's a mezzanine, but in here it only explains a single lobby level) - one painting in it says "Hans Mueller - Memorial Exhibit"

In the screenplay there's a whole sequence early on where O'Hallorhan is at a court hearing discussing the building code, and another one (right after Doug and Giddings pay a visit to Duncan) where he goes to his houseboat and sees his wife Dorothy and his son Michael Jr.

Giddings on the sprinkler problem: "That's top priority! Getting those alarms systems back on system. Along with the booster pumps. Right now we don't have enough pressure to supply the fire sprinklers above the fourtieth floor."

Giddings on Simmons: "If he changed a single spec, I'll personally drop him on his head from the hundred and thirty-fifth floor!"

The Promenade Room is depicted as a "magnificent dining room, cocktail lounge, and salon".

In the scene where Dan and Lorrie are trapped, Dan throws the chair out of the 65th floor window earlier on. Later on, "Her hair begins to smoke. Then catches fire. She screams, hugs the mattress closer, runs toward the broken-out window. She throws herself out, clinging to the mattress, as though it might become a glider to cushion her descent."

O'Hallorhan on the wind: "Tell him to move his barracades four blocks further out. We've got twenty knots of wind up here. There'll be glass flying all over town."

In the collapsed stairwell scene, the stairwell collapses from walls falling due to heat (instead of a gas line explosion like in the movie). Also:
"When the last of the plummeting pieces have fallen by, Craig [aka Doug] looks up worriedly at the collapsed wall which formerly isolated the stairwell from the elevator shafts on this side of the building. Then he looks down. The missing wall has exposed a terrifying chasm in which the stairwell and its floor platforms appear to be tiny abutments in the side of a bottomless canyon."
Also, they don't climb down on a broken railing, but on a fire hose. The hose breaks when Lisolette is climbing down it, but Craig (Doug) grabs her. As for the elevator shaft, you can clearly see it in the movie, but it's not the focus of attention like in here - I'm guessing the stairwell only drops a couple of floors instead of over 10 like in the movie, and so the 83-story drop from the elevator shaft would be far more threatening.

Right after Flaker says "We'll just trot right up the stairs", and O'Hallerhan responds, there's another scene of the Treasure Island air base, of Coast Guard helicopters taking off and the Glass Tower burning in the distance.

Flaker: "The winds are running at Force 5 up there at roof altitude."

The kitchen storage area is on 133 in the screenplay, and on 134 in the movie.

On the pipe shaft:
"This is the 'backstage' of the modern skyscraper - the open area running vertically the length of the building containing air conditioning, steam, electrical pipes, etc. Craig moves to a small opening leading upward through the cement deck above him. He disappears upwards into the frightening, open, vertical shaft."
then, "LOW ANGLE - MOVING SHOT WITH CRAIG climbing through the and between masses of cables, conduits and flues. He comes to a large flue at one side of the crawl-space. It rises through the floor deck above with inches of space around it. Craig crouches alongside the flue, tries to slip up through the opening in the floor deck above, but it's too tight a squeeze. He claws off the fiberglass insulation around the flue, widening the space, then pulls and pushes himself up through and into: A room full of water storage tanks. Craig emerges from the corner of the room, coming up through the deck alongside the flue, passes gigantic water tanks, disappears from SHOT."

Soon after that, there's a part where glass is falling from the building (with spectators are getting cut), and one shard slices through a police car.

The cemented door was caused by bags of plaster mix that were left on the landing near the door (with a plaster mixing machine), with some split open, and the contents accidentally wetted.

In the screenplay, the power goes back on again briefly (they get a backup generator going), but then goes out again (only on the higher floors) when the central core blows. A lot more happens then:
"A massive high-pressure steam line carrying power to the HVAC system buckles. A brazed expansion joint abruptly fails - the line explodes.
"A tremendous explosion, rocketing steel and fire and hot steam toward CAMERA, expands outward, collapsing the utility room. [the "utility room" here is an unspecified room in the residential area, supposedly near 110]
"As the explosion in the top third of the skyscraper hurls glass, debris, smoke and flame out one side of the building."
"The Havoc-
"A. Duct work collapses."
"B. Elevators plunge straight down their shafts."
"C. Pieces of cinderblock and pryo-bar tumble to the bottom from floors above."
"D. INT STAIRWELL that collapses. Firemen moving up a stairwell are plunged downward by collapsing stairs and walls falling in on them."

When the core blows, O'Hallorhan says "The Central Code just blew! All power above one hundred and ten is out again!"

When the Mayor and his wife are talking about their daughter, they end up going over and calling her; and earlier she says that her name is Jill.

In here it's Craig/Doug's idea for the breeches buoy: "O'Hallorhan, can you try to fire a breeches buoy across to us? Yeh - from the roof of the Peerless Building - right across the street. It's about a thirty-degree angle, but I think we can compensate with counterweights." - O'Hallorhan reponds with "Why the hell didn't I think of that? Okay, we'll try."

Says the 130th floor is the Upper Utility Room.

Simmons dies earlier on in the stairwell (when he tries to escape downward) from collapsing walls. Later on, it's Senator Parker who mobilizes the group of men and says "The women are gone. We're going next!". - Duncan says "Gary, you talk too much." and punches him. Then, instead of him trying to get the men out of the buoy like in the movie, he's one of the first to jump into it (since he's in what became Simmons' role) and dies when the buoy breaks.

As for the water tanks idea, it was originally O'Hallorhan's idea in the screenplay (unlike the movie) and later on Craig/Doug had the same idea.

When O'Hallorhan lands on the roof: "Behind him, a whole section of the roof collapses, almost pulling him with it."

The tank room (137) is called the Tank Storage Room

136 is "Utility Room" (the sign in the movie also says that), and they get down into it via a ladder from 137 and then go across to the staircase. (in the movie, they're seen going into the stairwell from 137).

When the tanks explode, the situation is somewhat different: "The roof fills with fire and builing smoke. The roof bows slightly upward from the pressure wave, then sinks in the middle. Sheets of aluminum curtainwall puff outward, split and peel away from the steel building frame. The concrete pan floor of the storage room rumbles and cracks away from its supporting beams. Huge sections of it fall to the floors below. Clouds of steam blow outward. - EXT. THE GLASS TOWER - ANGLE FROM STREET LEVEL - NIGHT: Explosions ripping off the top floors - water cascading out as though a waterfall has deluged the peak of the building."

Also in this, Carlos lives, and Harlee is tied to a grand piano which gets washed towards a window but gets lodged in it (he survives).

Near the end, Craig/Doug says this: "I'm asking! I'm staying here - and putting this one together again! The right way! The way it was supposed to be - from the very beginning."

At the end, O'Hallorhan and Kappy are hosing down the promenade room at dawn, and O'Hallorhan's wife comes and brings them food.

This funny thing is said at the very end (according to Michael Jehn, this was taken from the book The Glass Inferno):
"A stray piece of wood glares. A gust of wind blows in through the ruptured walls, fans the tiny flame a moment. Then the wind passes. The spark fades, turns black, and dies." - then there's a camera pullback upwards (so that it's looking at the whole building from above), and then fadeout.