I feel dumb as a brick asking, but. Are there any drop in replacements for the "Corsa" engine Cen runs in the Genesis, and its relatives?

Preferably with pullstart, and of course, a bit more "go" isn't a bad thing.

If i cant find anything reasonable I'll grab a crank-case & shaft of ebay, and see if i cant get some more rpm's out of the engine with a bit of grinding.
B!