I'm thinking more like Mopar had more Nickel in them to begin with and not like any others had any more or less for the la.
I do believe that the 318 from 67 to 71 to 72 have thicker cylinder cores... unlike 302 heads which are thin pieces of **** but some people just 'Romance the stone' over anyhow due to their limited production...in which Chrysler killed them realizing that they were a piece of **** and just went to a magnum head with a little bit bigger volume intake port and better chamber.
I can about guarantee if you took an engine and swap just a heads from 675's to 302's that they wouldn't make any more power.
Maybe 4cc worth of power in squeeze...but then loses it from the shrouding and bulbous valves stem. I know of 2 sets, on running motors...n I bet they're cracked. Why bother. I could get them, port them up and no one would want them...not when it comes to spending on them, that's how not good they are.