Any particular reason you need a DOWNLOAD? I find it exceedingly inconvenient to climb out from under the truck, turn the computer on, get greasy fingerprints all over the keyboard (and my 2 year old -- he'll want a hug), navigate through a menu, get what I want, print it out, and go back to the truck, when all I really needed to do was turn a page....
And you won't find the factory manuals on CD from 1991. CDs were expensive and not very common then. If you do find one, it will be an after-the-fact scan, and will be much less readable than a printed copy as a result.
The typical Autozone (Alldata) CDs are virtually identical to subsets of the Haynes manual.  Without the photos.