Too true Pete. With the head bolt, I was thinking as long as theyere eithin a couple mm of working, you could weld up the mounting holes in the head, solid and then re drill them slightly offset. I think all of these design differences and compromises are whats kept this idea in dream land. Personally Id rather buy one of those repo Dallara heads and other parts.
aarpcard: I cant really speak for others on this topic as to why or why they wouldnt want try this. For me though, bragging is not one of them. I think the original idea was spured because the heads look so similar, and particularly the 2v early 308s being considered. A bolt on, cross flow head with larger valves then can be made to fit into an X head and potentially less strain on the valve train. Thats all very enticing....probably not practical unless your a Sultan, but enticing, none the less.