Fstfish66, my dad got the NASCAR heads from Carl Kiekhaefer founder of Mercury Marine Outboard motors. Carl raced Chrysler 300's and Also a few Dodge D500's around 1955 to 1957. I believe the Kiekhaefer team won 2 championships, he was the first to use team drivers and matching racing suits, along with other improvements that NASCAR follows today... He changed the sport.
These heads were cast in his foundry with larger valves, larger intake ports, and larger and rectangular exhaust ports (not round like factory heads). They don't have a water passageway that goes thru the intake manifold, so when they were used you really had to warm the engine up first, and have a carb plate insulator under the carb. Like mercury marine, we are from Wisconsin too, and my dad picked then up from Carl in 1961 long after they stopped racing NASCAR. The heads were just sitting idle on a shelf. If I find the side by side picture showing the factory heads and these heads, I will post it.
It's just that Chip has really peaked my interest in this motor instead of the 340 I was thinking of using. It would be a show stopper in a 1938 Plymouth P-6 Coupe