factory 72 340 pistons???

That looks like an aftermarket piston. All factory 340 pistons had two valve reliefs. The 72/73 were flat tops, the earlier pistons were domed. Heights are different between how deep they set "in the hole", and from the wrist pin centerline to the top block. P/N 3004571 (std) 3004572 (+.020) and 3004573 (+.040) for the 73 pistons.