you can use hypereutectics pistons speed pro h581cp 119cc/10.2cr get a small roller cam hyd or soild if you have the money and rework the 781 heads you can put the big valves in but what rpm are you running this to ? i would use all stock bottom end recon the rods arp bolts and spend your money on the cam and some head work i would say if done rigth maybe 450+hp this has alot to do with your vacuum talk to cam grinders i would look at maybe a custom grind i would build for tq not hp