That is a interesting read about the alternators on that TurboMinis link.
Hopefully downsizing my alternator will stop from hanging out the front.
I just went and bought a 91 Daihatsu Charade Alternator (Denso) that has a 4 groove belt the same as the waterpump belt!
(relevant number is 27060-87721)
Good for 2 reasons, I don't have to sort out a new pulley to get it to work and I now know I have enough belt to drive my alternator properly.
Not sure how well it will fit and I won't be able to find out for a while I'm afraid, as I'm not near my mini at the moment.
Worst case it might help alleviate clearance issues in and around the Brake master cylinder if I have to mount it up there.
The Micra crank pulley is 88mm and the alternator's pulley is 45mm (by eye) so the alternator should be doing close to twice the speed of the crank which probably means it might be able to use a smaller pulley again if the top rpm is near the 18000 suggested on the turbo minis link (this was for Brise though maybe they use better bearings).
I haven't been able to find out the diameter of the charade's crank pulley so not sure how fast the alternator is supposed to spin...