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