I don't think they actually had their main guns mounted, which makes them an odd variant of their own. Put it to you this way - I didn't see any intact MBTs in footage or pictures of the Krispy Kritters incident. I did see the M88 and the engineer variant of the M60, though (can't remember the designation offhand).
The M60 variant you saw is a combat engineer vehicle (CEV) with the main gun replaced with a short barrel gun for blasting through fortifications at close range. Utter overkill in that situation.