It's been my experience that vintage Conns play very well on vintage Conn mouthpieces. If you can pick up an old Conn 4 cheap, give it a try. I bought a '60 Conn 6B Victor, and tried my 3C (my usual trumpet mouthpiece) on it, and it didn't play as well as I hoped it would - intonation issues and some stuffyness. I bought an old Conn mouthpiece just to see how the original equipment piece performed and it plays great. I'm not sure why it works, but I'm sticking with it.
