Does it have the big keyboard hole in the back of the case? About the size of a quarter? That would be an AT motherboard.
I think there is a guy in these forums who has some socket 7 boards for sale.
http://www.techimo.com/forum/t80166.html
The FIC Va503 he has was one of the best of the socket 7 boards...lotssssss of jumpers though.
AT boards are getting hard to find.
If I were you, I would go to
www.anadtech.com and look in there "sale" forum where people sell stuff. Go there and do a search for "socket 7"...youll probably find something.
JP