Many of the V4 engines do have more mains welded into the block. Welding more mains into a GMC block came up a few years ago, but no one was prepared to actually do it that I know of. And so as far as I ever heard no ruling was made as to legality of that modification. As I read the rule book all it says is that the head may be cast, billet or weldment. That pretty well coveres it as far as I know. I see nothing about head bolt arrangement except that OHC heads can not be used even if they bolt on. So I would say "Go for it." No body in tech is going to be impressed if you tell them "Rich Fox said it was OK." Speaking of welding what about some of the flatheads (Ron Main amoung others) that have had the airflow greatly improved. That's not so far removed from using a later stock (Cheap) head.