You'll have to search around and find those engines.
The 1PG engines are real old, and their performance was ok but used a points/condenser system.
The 2PG HO engines were only produced in 1988, and they are next to impossible to find.... Their popularity today is about on par with a 454 big block, but back in the day they were just cool engines.
I think one of the best engines to use is a 35hp vanguard/briggs engine. The rev kits and other mods available for them can help produce upwards of 60hp out of that little engine.... They are more expensive than a Honda, and the Honda engines have some nice mods for them also. Brand loyalty/recognition, fabrication skills, and time are big factors.
The Briggs or Honda V-Twins will cause you to loose reverse, due to those engines being 4 cycle. You will have to align and level the engine to the rear driven clutch (too much of an angle can flip the belt). It would take a lot of work, but the ability to dig holes is what counts
