To the best of my knowledge, the TRW pistons were not available from Chrysler. Very possible if you went to the dealer parts counter, and asked for .030 pistons, the parts guy would order aftermarket TRW's for the customer. Back in the '70's I ran NHRA stock elimiator with 2 1965 Valiants, One had a 170 slant and one was a 273. The slant had .020 stock pistons, as NHRA dictated OEM pistons. They did allow .030 oversize, but I could not run them as the factory/parts counter only had std, .005, .020 and .040 available. I cheated with the 273 and ran .030 TRW's.
I will get the OEM part numbers a little later.