Which heads to run on 340

Alright so im currently planning a 340 build slowly gathering piece by piece sense im in no big hurry. I had a set of magnum heads i intended on using but after a trip to the machine shop i found out there cracked in between the valves in the combustion chamber on both heads. I have a set of 360 J heads if i had the J heads milled and the valves punched out to 2.02 intake valves will that make the comparable to the 340 X heads or which heads so i try to find? Any and all help is greatly appreciated! Thanks Guys!