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

True, some 72's came with forged cranks but most had cast. I dont think it was a 4 spd vs auto thing, just early production using up the forged cranks they had on hand.
I daily drive a bone stock 73 (except air gap intake, avs2 carb) and I can assure you the low compression 340's are still strong runners. Almost the perfect engine for a street car....as far as being practical.
All things equal, if you bump the compression up to 10-10.5 the 340 becomes a whole different animal.
I love 340's. In my opinion its the best small block ever made.