I would build the k-341 Randy. But if so desired a 12,14,16 hp kohler all the parts interchange except the piston and head. To make it easy on your self though use a starter on the engine. You can build it for a starter cart but i personally think they are a pain. 16hp kohler with a long rod, short piston, a good .340 grind S/A cam. Vogel has some really good grinds. 25lb ring gear flywheel with a recast head from vogel you will have a good running machine. You can use a good billet head from Vogel if the rules allow it.