uh....u can make decent power out of the stock ls pistons...get a thinner head gasket. i remember readint somewhere that the compression would b right at 10:1 with the ls bottom end (not sure where i read it tho). ive been doin research on this bc im doin the conversion soon...but ya, thinner head gasket would put u at more compression than a stock usdm gsr (if what i read was correct). i say keep addin ur bolt ons and get a tune n theres no reason why u cant get close to 170hp on stock cams.