For laughs I've been running a 486dx/33 (intel) at 66mhz in a dell box.
The only mod if the heat sink is a moose I had and its attached to the
chip using a BEo filled thermal epoxy. Runs cool and it's solid.
I've tried that in a socket5 Mb I have using a 486dx2/50 at 100mhz, seems
fine after three months. The cooling is not big a problem.
I consider both abuse, but hey I have a few. Besides I've done that before
with 8085s and Z80s with no ill effects.
Allison