One other thought about rear sprocket replacement, Phil Bleazey does a belt drive to chain drive conversion. I think that, at the moment, it is more than a nuts and bolts job but it may be worth a look on his website.
http://www.bleazey.co.uk/M3W.html#reason . It's always interesting to have a look at what Phil is up to anyway. If you do end up with a new steel sprocket from a Morgan dealer, don't dispose of the alloy one, I am sure it will come in handy for a chain or Supermax conversion at some point.
