Nice write up Dogdays.

I kicked around the Poly head to Hemi block idea years ago.........never got further than looking up part numbers. As I only got that far I don't have any hands on experience but it looked possible.

One of the things I came across was that the "triple 5" heads used on the 56 354 (and some 331?) Hemis flowed better than the stock 392 heads. Because the head swap was popular with the hardcore hemi racers, aftermarket spacers were available as far back as the early 60s. In fact those spacers are still available from Hot Hemi heads. When I checked intake gaskets they showed the same part number for both the Poly and Hemi, indicating the port size and shape were the same and at least on paper making the swap possible. The one thing I I didn't readily find that would be required were off the shelf pushrods which would have had to be custom made.

To me, the story of a Hemi to Poly head swap still seems feasible. Whether it was actually ever done.......who knows.