Looking to put a wiseco 76mm oversize piston in an 87 Xr250, I read that the 1mm oversize 84-85 twin carb piston is 76mm and will work fine? Have looked at cometic gaskets and I'm confused. Whats this difference between a SS and CFM head? there seem to be gaskets listed for 86-95 bikes with both head types?? also there are 74mm and 78mm gasket sizes which one for the 76mm piston?