Hi Bonny,
Those as you say are from a late ('58 on I think) B31 / B33 ..
A while ago I almost bought (sight unseen) an alternator A10 with a few non-standard bits fitted.. In the end I chickened out as it was a bit too close to the price of a standard unmolested A10 ... He was a nice genuine bloke, I often wondered if I should have had it, just for the rarity value..
Anyway, I've found a couple of pics he sent me ( the alternator didn't work - hence it wasn't fitted - see pic) . It also had a dynamo, but that wasn't working either!
I recall him saying that the crank was special for this model & if you look at the photo the shaft does look pretty long - I'll leave it to the experts out there to decide!!
Hope these help or are of interest. I include a pic of the engine to show the A10 primary side..
Chers,
Adrian