And you'll have to pardon my ignorance of the Intel
parts after the 8085,
but why wouldn't a 386 work if the 486 works?  (Other than the speed
difference.)  It has always been my impression that few OS's/applications
need whatever extra software features that differentiate the 486 from the 
386.
I believe the 486 was supposed to be just a 386 with a built-in math
co-processor. Then Intel came out with the 486SX. Which was really just a
broken DX, a 486 in which the built-in math co-processor didn't work.
        -- Kirk