I'm hoping this isn't a stupid question, but can't you just swap the v-belt pulley onto a later serp-belt alternator? Are the offsets different? I don't know for sure, but I thought that was the normal way of doing it.
My '95 motor has the serp setup, I can take a few measurements to see if the 80A Bosch is fully compatible mounting-wise with the 105A Valeo. IMHO I'd stick with the 80A unit to improve fuel mileage.