Hi Ray.
I don't think you have missed anything, other than me having a senior moment
Being that an alternator generates an AC current that is then rectfied into a DC current then yes it could spin either way.
One thing I am unclear of is. Will any reverse spin on the alternator change the forward current flow through the rectifier pack ? ( I didn,t pay attention to the theory of rectifiers at school )
Oh bugger I have just confused myself there.
I doubt the pulley retaining nut would be a problem. Nothing a dab of loctite woldn,t put right.
I mean that in the best possible taste & no pun intended.
The weight of the unit is 3.25 Kg with the pulley fitted. This compares well with some of the competition ones that I have seen (2.7 Kg , but that figure is probably minus the pulley)