[Lynn Eades]

Get the armature checked out, If it checks out o.k., you can get the commutator turned.
Then you need to under cut the mica (make a tool from a ground hacksaw blade)
The problem with the generator is that it has a bush at the rear. An over tight belt will quickly stuff the bush. Then the armature "poles" (hits the pole shoes) and burns out the armature (and regulator?)
The fan extension dis engages that side load from the generator bearings and makes the geny more reliable.
Just make sure that when you have the geny rebuilt, that you pair it with a good (new or tested) regulator. When one fails the other is usually a casualty as well.
If you go over to Lucas bits, it will all be easier where you are.
If its just brushes and bearings it is easy enough.
The alternator is reliable as, but you will need a very small pulley to turn it fast enough, and then the belts will likely slip because it takes a lot to drive the big (important) fan.
The fan is also a weak area, so check it for cracks etc. while you are in there.