fyi, Thought I'd post my 'final conclusion' after a few days of searching for the right answer and coming across numerous, cumbersome processes to get AV3x on to 64 bit Windows 7. I stumbled upon a pretty obscure but seemingly straight forward answer, somewhere... You can simply download a 32 bit 'installshield engine' - setup32.exe - and use that to install the AV3x files from original installation media - instead of the 16 bit 'setup.exe' that normally comes with ArcView 3x... Put setup32.exe in the same folder as the ArcView 3x installation stuff, double click, and it installs normally. You might have to run that program in Windows XP compatability mode...
I had used a version of AV3x that I copied from an XP installation, but ran into a few problems here and there. For example, the projection utility wouldn't work. Trying to fix that I got fed-up with all the 'change the registry' stuff, copy this, copy that - so I tried this setup32.exe way. Seems to work so far, projection utility works, though there may be some issues with that that I haven't figured out yet. Everything else I've tried works, though granted, I haven't done a whole lot yet...
edit: Here's a link to the page I found that talks about using Installshield 32 bit vs. 16 bit, which includes a link to "setup32.exe", scroll down to "Installshield3 shortcut" at that page:
http://www.reactos.org/forum/viewtopic.php?f=22&t=10988