I found this by combing the various abandonware sites:
http://ds.old-games.com/199f3e523b/f.../motorcity.txt
If that link doesn't work (it may be classified as a download for some reason), then you can find it by using this link instead:
http://www.old-games.com/download/4346/motor-city
This is only the portion of the manual about the game itself. It doesn't include any of the historical information. I have to admit, it's not as informative as I hoped. However, since others have asked for it, I thought I would share the link .