Yeah Cab it can get a bit confusing trying to keep track of all the engines Chrysler, DeSoto, Dodge and Plymouth produced during the 50’s. Here’s a pretty good breakout of the 50s Plymouth poly engines.
https://en.wikipedia.org/wiki/Chrysler_A_engineThe Chrysler 301 Poly (Spitfire) engine shares nothing with the Plymouth 301 other than the displacement.
The Spitfire 301 is based on the 331/354 HEMI block (with smaller bores) and the blocks are externally (dimensionally) the same.
On a side note it’s amazing how many 1957 Plymouth 301s are misidentified as 318s by their owners.
