I think I remember reading that the
aluminum Magnum heads
had an extra thick deck and could stand 0.060 inch of milling, but i dont remember seeing anything about the stock cast iron Magnum cyl heads.

Here's a few links that are worth a look:

http://www.hotrod.com/techarticles/engin...ge/viewall.html

http://www.moparmusclemagazine.com/techa...ck/viewall.html

http://www.popularhotrodding.com/tech/0507phr_mopar_magnum_engine_specs/