Cam lift question

I have a 360 with magnum head conversion. I'd like to use a comp xe-268 cam with lift of .477 intake and .480 exhaust with 1.5 ratio rockers. The Magnum has 1.6 ratio rockers. So the question is will there have to be machine work on the heads at the valve stem area to use this cam? Seems I heard the magnum heads would only take around .500 lift without clearance problems. I don't want to disassemble the engine at this point for the cam change, but I really liked the xe- 268 in a 318 I once owned.
Bob