If you have a bone stock 1972 460 with 8:1 compression ratio, then putting on the early-style heads will give you about 9.2:1 compression ratio.

You need to see which casting number is on your heads. IF you have the D2VE-AA heads, then the valve train assembly is different than the early heads from the 1970 car. Assuming you have D2VE-AA's and will swap to D0VE-C's, then you will need to swap over the heads, the pushrods and the rockers. The valve train components must stay with their respective heads because they are not interchangable between each other.

The horsepower rating system changed from brake horsepower (BHP) to Society of Automotive Engineers (SAE) in 1972. Your engine will have perhaps 300BHP with the head swap and good tune...somewhat more with cam and carb, etc.

Paul