LA and Mag heads are bolt-on interchangeable as far as the block to head. Intakes, rocker oiling, etc are different but no difference in the head bolting to the block. There are some problems trying to get a later block to get oil up to the LA rockers, I think that's what you saw in the link. The real question is why one would want to put an LA head on a Mag block unless they were W2s or something like that.

R.