OK. I took the rotor nut off this morning, and nothing amiss with the rotor - timing marks line-up with the keyway slot. This meant it was the position of the keyway in the crank. It is a Maney crank, so I gave Steve a call and all was explained. Apparently, Norton changed the position of the keyway over the years. Obviously, with such small production runs, Steve had no choice but to simply pick one of the iterations to follow - I just wish he had told me when I bought the crank!!!
As far as my carb set-up is concerned, it is just a Sudco off the shelf version of the twin Keihin FCR 35mm flatslides sold by CNW, that I bought off eBay. I won't know how well they are jetted until I start riding, but they are supposed to be jetted for an 850. I already had the manifolds and connectors that CNW use and the kit contained everything else. They are a tight fit; and presently are just a little too close to the frame downtubes, but clear the webbing ok. I am going to have to find a way of bringing them nearer to the head. On a Roadster, the carbs obstruct the RH petcock, on my Interstate, the bottom of the tank fouls the twin cable carrier. I have resolved this problem by drilling out the rivets and lowering the cable carrier to the lower set of location holes and converting to a single pull system.
Cheers, Bob