CALL, Jack.@ BIKEBERRYS.com they Carrie both low and high .160 dome pistons. It's what you'll need if your plannig on using a high comp. head down the road . If your running a long rod the piston WILL HIT THE HEAD, but this ok . All you have to do is one of two things , #1 get one those this a$$ head gasket and use RTV W/COPPER the base gasket. OR #2 use 2or3 base gaskets &2 regular head gasket. I did #1 UNFKN compression ! It's so high my pullstarter cord snaped. You'll need to run 24:1 mix and a BR10HIX NGK IUIDIUM PLUG for 3 resons :A, your bearing will need help B, The coldest high spark plug for high comp engines need more fire, (get or build a jaguar CDI and coil) C. And last the rich mix will help you from OVERHEATING.400+degrees not good. I run a TTO Tach &Temp gauges .