what are you looking for cr if the bore is good you can use a 396 +0.30 kb makes some but the cr may be low with the big chamber head so look at the speedpros or trw they are not cheap the old 396-402 pistons cost the same or more than 454 you wil need the 396 11to1 to work in them heads to get the cr up to make it run and they will not be that hi on the 781 head and i think $400 a set but when you get past that with the rigth cam it will run geat.