I appreciate the information from everyone.
It appears the Pro is a longer recoil assembly, to go with the longer barrel, and isn't interchangeable with the standard Hellcat.
I talked to Powder River Precision, and their president told me perhaps next year they might consider making something...
I'd like to replace my Hellcat Pro's plastic guide rod/ recoil spring assembly with a tungsten/steel one to add more weight to the front of the gun.
Does anyone know if the standard Hellcat's recoil spring assembly is the same size/length, as the one in the Hellcat Pro, and interchangeable...