Early 72 340, is this one of the de-tuned ones?

Exactly. Also sometimes the ridge "look" can be deceiving. Best to measure first. I've seen a few that were still in spec even after honing back round. It's rare but it happens.
With all this talk about Ridge I decided to add some pics of the pistons to see what you all think?

piston1.jpg

piston2.jpg

piston3.jpg