I really doubt if a complete flathead repop... even with the Ardun-style heads... would be accepted by builders used to more modern power.

I had a couple buddies in the late sixties who built flatties with all of the usual bells and whistles, and they could not even come close to the 327 smallblock Chevy power in my toys at the time!

I respect the basis that they made for hot rods of the fifties, but today they would only make good paperweights. You need to be able to run seventies on the freeway, and the imports would run all over you at stoplights. {:-(