People say cr is one of the reasons a magnum seems responds a bit better than a LA engine to a basic cam, 4bbl, header swap, I don't know that for sure but we do know the magnum response well to these mods and can get over 400 hp without any head mods.
I'd like to see similar cams etc.. ran through an LA an see what it dynos. Seems like it's probably about 20-30 hp down to a stock magnum.