I probably don't have much advice for you, as I'm not a expert on these engines. I don't know what the difference is between the heads, but they probably won't give you trouble to use them. I kind of think the main difference is in the block (bore and stroke). If you are not trying for speed or performance and your remaned engine is running good, you should be happy with the stock 429. They are a good engine with lots of power already, and you'll probably have lots of other things to worry about on a car that old.
