I think another point that has not been discussed here is porting. W2/W5/W8 etc. heads work best when ported. Sure, you can use them OOTB but Mopar realizes that people are going to port them for maximum efficiency and power.
That is a good point you bring up. For example, my fully ported J heads flow 20cfm over my new casting W5's. There is plenty of meat around the valve guide area. They are meant to be ported!
