Stage 3 big valve head is must as stock valves bottle neck at around 250bhp, Newmans cam i'd agree with but not double valve springs they specifically say not to use them! Even a Stage 3 T3 (48/55) would not flow enough for 300+bhp i'd look at something bigger! Dont know what 803's are good for. Pistons, rods, yup and arp bolts to hold it all together!