I would opt for the 572 (or bigger) for the torque and low rpm, plus you can get away with a less aggressive valvetrain for long life. I know nothing about them, but want to follow this thread to see what folks think of the Indy Cylinder head Legend stuff. We have a lot of Indy dealers on hear, so you wouldn't have to deal with Indy direct. Fast68plymouth is one, Todd Marsh I believe is also.