You don't need counter rotating engines in the first place. The Only Full sized airplane in WWII that had counter rotating frops was the P38. Every other one rotated in the same direction. You can't reverse the front housing and back plate on the old OS FSR's. The bolt holes aren't as deep on the rear cover. Even if you could it would still rotate in the same direction. Timing is controled by the crankshaft. You can turn the front housing 90 degrees in the direction of ratation and the engine will run backwards but with a power loss. Best bet is to buy a reverse crankshaft.