Tony, this could be the reason. (The quote below.) On a 360, I can only guess it doesn't matter much on a mello build. They came stock on some 360's (E-58's) I'm also guessing it would matter on race/performance builds as per Jim Szilagui in his book, "How to build big inch Mopar small blocks." As mentioned earlier in the tread.
I haven'y been there myself. 360's yes. 360 on a dyno, no.