Used an alternator from a Datsun Stanza (our paddock basher), although we had to do some handy work to make it fit.
The adjustment bracket had to be extended to be able to stretch out the fan belt enough to be tensioned. So the bracket came off and I cut it down just into the adjustment range.
Then a piece of steel of similar specs was welded in (using Dads handy skills) behind the split bracket to extend the overall length.
This is the finished producted painted.