 tisco pistons are fine.one M I have has 00 cracks in the head daily runner at 00 hp it is ok. most power is in the cam have a new one ground for the hp you want. don't plane the head you need the cc's for fuel mixture. make the compression up with the thickness of your head gasket. use a LP intake and exhust. drill the carb out. open the head up but don't polish. you should have a strong runnin M. I have six of them for play  