you will need to have them opened up to the larger 2.19 valves. You would really be better off finding some 049 or 781 castings if you ar gona go the oval port cast iron route. They are still small valved but have the better chamber design. They are fairly cheap if you can find em....but still by the time you get em all done up you could almost buy some aftermarket heads. A 427 can be wound up pretty tight with good parts.