What year is your Magnum? Earlier models have provisions for LA heads which gives you more options. My last build was a ‘94 and I was surprised to find that it had LA oiling passages in the block.
I am not sure what year it is. Is there a casting mark that makes it easy to tell? I am not sure I want to go to LA heads, I just want a good head that works well and doesn't require an expensive rocker set up.