Stroker 400 that has been sonic tested before building, bore to the smallest size needed to clean up the bores and use a 4.250 or 4.300 stroke crank with 6.7 or 6.8 long BB Chevy type forged steel rods, 10.5 to 11.0 compression ratio for pump gas with 1/16,1/16, 3/16 standard tension file to fit moly rings and a set of ported 440-1 heads with 1.6 ratio rockers and a Indy 400-3 intake and a 1050+ CFM Dominator carb and good fuel delivery system, solid roller cam with between 255 to 275 duration at .050 with as much lift that you can get