Windows 3.0 will run on an 8088 or 8086 with 512Kb of memory, Windows 3.1 won't (it requires the 'real mode' that 80286s have).
If Windows95 was running on a bridgeboard then it must have had a 386, you used to be able to get accellerators that would take any 8MHz 286 to a 16MHz 386 - if you could find one it'd work in a bridgeboard, though if the clock frequency was different it might take some persuasion!
