I don't think any of the now in production repro #3 frame model cylinders will interchange. They are all longer to accept the modern chamberings. In the re-design process to lengthen them, the original gas ring at the front went away, and the overall length (frame window opening dimension) is greater. The diameter of the cylinders increased by about .075" also. The first repro to come out, The one made by Armi San Marco, was the closest copy to the original I understand, but the cylinder on that one was lengthened also. Not sure about the diameter though. The extractor has some differences from the original also. Wether any of the repros could be altered to fit,, I do not know.
