71 340 Compression Test

Just remember that you change the damper and flexplate/flywheel and or TC if you go from a cast 340 crank to a forged 340 crank. The cast crank has balance weights on the damper and flexplate or TC (or flywheel), and is known as externally balanced crank (which is in reality is actually just partially externally balanced).

I see such cranks advertised on places like CL. Caveat emptor....

As for running the higher SCR on iron, that may be fine depending on the cam. Drag eneinges run 11-12-13 all the time but with big cams. The key is your DCR. What do you use this car/engine for? Will you be changing the cam?