Many many years ago many of us got ripped off by Direct Connection on the P400 series pistons. They were advertised as 11.5 compression and the TRW’s were advertised 13 plus compression. Those of us, me included were street strip racers and paid the extra 200 plus dollars for lower compression. I ran 11.80 with them in my street strip 340 duster back around 1980 or a hair earlier. My buddy has bought several used sets over the years and lots of times both part numbers were in the group.