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