Shop air dilemma

A smaller engine would be great
Smaller than what?
I have a few old kohler cast iron engines around, and an 18 hp opposed twin too. I wouldn't mind finding a big enough compressor to drop one onto that would eat up all the HP whichever engine I wanted to use, would eat up my 5 hp gas one would be a decent paint/spray rig I think, or great for airing up tires. It barely handles my 1/2" impact. My 8 hp gas one is a little better, faster recovery time than the 5 hp unit but a little smaller tank too. I'd like to find a 2 stage compressor with a dead motor and an 80-120 gallon tank that I could put one of my heavy old kohler engines onto. When looking for a compressor it is rare to hear someone say that theirs is too big,and when you do usually it's a "not enough space" issue more than "too much air for my needs".