Ok yes all motors require the same thing in order to gain compression numbers. I've just heard that it takes a little more work with a big block mopar. That info is coming from a guy who has built these motors since the mid 70's.

Now it cannot be that hard to get 425 hp out of a 383 big block. Plenty of factory big blocks were claimed to produce that much when they were actually making more. I am not going to build a 400 motor unless I really have to. I want to keep the motor the car was born with. I can understand going with closed chamber heads, 484 lift mp cam, and a good set of 3:55 gears. But I'm not going to rebuild a whole 'nother motor if the factory block is in excellent shape.