70" 340 vs 72" 340 specs please

The only difference were pistons, intake valves to 1.88, Carb and intake, and exhaust manifolds. Somewhere in 72 the crank was changed to cast, but my two 72 340s were forged. If the crank is cast, then you need cast 340 damper and flywheel/torque convertor. Early pistons with the stock cam will ping and blow head gaskets.