R motor wont go in. Tried that for my x. I think its clearance issues for the exhaust. I think the r frame is a few inches longer in the engine area or something like that.
For about 5-6 hundred dollars you can make the x pretty fast....well faster than a decent modded blaster. 12:1 piston,race cam,heavy duty valve springs, exhaust pipe and a bigger carb. Oh and a decent gasket set will be about 80 bucks.
oh yeah and check ebay. I got my toomey for 150 on ebay.