Muscle Head Stage II: “Pro Mod” Program #01, 2.400″ x 1.900″ valve dia, 97cc chambers. Iron valve seats, .025″ Jr hoops, All 9/16″ Head stud inserts. (pair)

Muscle Head Stage V: Program V3-P1-F12, 2.450″ x 1.900″ valve dia. 102cc chambers. Std Copper intake valve seats, B5 Exhaust valve seats, .025″ Jr Hoops & 9/16″ Head stud inserts. 2.600″ lifter spread, 12ø Exhaust Flange. (PLR only)(pair)