@NightRunner , I’m not sure I can be of any help here with the swap but I am looking forward to this thread and your journey on this. I would love to see this come to a fruitful end!
The Magnum engine is much like the Vortec engine in the evolution of engines. Your limited on heads and intakes. Swapping to an earlier LA head and intake will require that you use what your already used to with the Chevy, pushrod oiling. Just make sure the LA rockers are capable of oiling via the pushrod. Headers will be interesting.