The NHRA spec for the 1970 383 is .004" below deck. I guess you could cut .100" off the deck. I know they used to cut that much off the SS Hemi blocks, but not sure about the 383 blocks.

They also list other legal pistons for Stock. I don't know if all these will work for Pure Stock?

383 60-71
TRW L2315F
TRW L3057F
SEALED POWER 2257P
ROSS 74233
CP PISTONS M17-CP

4916280-CHRY-70[1].rtf (292 downloads)
Floyd Lippencott IV