Two things...
Far as the heads go, I was referring to 1:1, but all you'd need to do to represent 'em on a model is paint them whatever you use to represent aluminum. They're designed to bolt in place of the cast-iron originals and accept all the factory stuff like manifolds, alternator, PS, AC, etc.
Thanks to CanCon, we know it's not a righteous 472 in the Johan kit. I wasn't sure whether the Olds from the Toronado was dressed up to look like a Caddy, or if it was the other way around.
As he said, it looks like the Ford (non-Boss) 429 could be reworked to make a reasonably convincing Caddy 472/500 without too much difficulty.