I was told the following story by one of the techs on the Direct Connection tech line back in the early 70's. True?
After NASCAR banned the Hemi (or at least limited its fuel allocation) and the big teams went to small blocks, but there was not yet a race block from Chrysler. So, the story goes, Petty Enterprises bought up a bunch of AARs and T/As just for the T/A blocks, which were much stronger. They put the engines back together with stock 340 blocks and resold the cars.
This, of course raises the question: Didn't the factory have any six pack blocks to give to Petty? I think NASCAR went to small blocks in 1972, so maybe there weren't any left. First race block was '75.
Bob