I am slightly late to the party — this happened last week — but here is the long-lost December 1977 version of Zork.
This repository contains the source code for a 1977 version of Zork, an interactive fiction game created at MIT by Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling. The files are a part of the Massachusetts Institute of Technology, Tapes of Tech Square (ToTS) collection at the MIT Libraries Department of Distinctive Collections (DDC).
I don’t believe anyone has tested it under Confusion (the MDL interpreter, the same thing I used to play the later version of Zork for All the Adventures) but I see no reason why it wouldn’t run.
ADD: I wanted toss out something I noticed from the source code. The naming story behind Zork is circuitous — it started as Zork, got changed to Dungeon, then back to Zork. The December 1977 version is named Dungeon!
WELCOME TO DUNGEON
DUNGEON is a game of adventure, danger, and low cunning. In it
you will explore some of the most amazing territory ever seen by
mortal man. Hardened adventurers have run screaming from the terrors
contained within!In DUNGEON the intrepid explorer delves into the forgotten
secrets of a lost labyrinth deep in the bowels of the earth,
searching for vast treasures long hidden from prying eyes, treasures
guarded by fearsome monsters and diabolical traps!No PDP-10 should be without one!
DUNGEON was created at the Programming Technology Division of the
MIT Laboratory for Computer Science, by Tim Anderson, Marc Blank,
Bruce Daniels, and Dave Lebling. It was inspired by the ADVENTURE
game of Crowther and Woods, and Dungeons and Dragons, by Gygax and
Arneson. DUNGEON is written in MDL (alias MUDDLE).
Additionally:
>ZORK
That word is replaced henceforth with DUNGEON.
>DUNGEON
At your service!
From the 1981 version:
>DUNGEON
That word is replaced henceforth with ZORK.
>ZORK
At your service!
Renga in Blue 
Oooooo a nice piece of history saved there