This is a popular combo for us. Starting out with a GM block, we install billet splayed mains caps, toss in a Callies 3.875 stroke crank, and hook up Manley rods and Diamond pistons. Topping it off are TPIS AFR heads, TPIS ZZ-X hyd. roller cam, Comp Cams pro magnum 1.6 rockers, Canton oil pan, Fluidamper harmonic damper, TPIS miniram, and TPIS 52mm throttle body. She dynoed at 555hp @6400rpm and 490 ft/lbs. @5600rpm.