I have a very well worked over set of 440-1 heads with 2.300 intakes, which are the same casting as a 572-13 with the following exceptions. Moved exhuast valve to allow a 2.30 or 2.35 intake valve. rolled 2 degrees for a touch better breathing. Those heads have been a touch better at making power over a 440-1, but not a lot. They just don't have the port csa or volume to feed a BIG motor. My guess is they will be pretty much all done increasing power by using a 572 cube shortblock. I run 528 cubes under my 440-1s and I don't see many guys running that much faster per weight carried, and with 572 to 578 cubes.