I don't know. My information is second hand.
I had a wonderful magazine article that I lost a couple of years ago. Somebody in England was building complete reproduction Series B bikes because he had a set of molds. The article was actually about a head-to-head comparison test between the Vincent Reproduction and a Yamaha V-max. Oddly enough the Vincent handled better, and it's 1/4 mile times were pretty close. The V-max beat it in the top end though. The Vincent just wasn't good for much over 120 MPH, while the V-max would push 140 pretty hard. That is, if you had the balls to push it that far.
I also read an article about an Australian company that was building complete Vincent motors, but had made some slight changes to the engine. It had a better alternator, new transmission, and an electric starter, but otherwise was pretty much the same. I saw some engine and bike pictures and they looked great! But like Norton here in Portland I don't think they ever got to the production stage. I haven't been able to learn anything more about them on the web.