The 901 is a better choice for beetle conversions. The advantage of the 915 are more ratio choices in stock and aftermarket form, and more chance of finding a used LSD for a decent price. The 915 is much wider in the front requiring more clearance to fit into the beetle chassis. Stick to the 901 is the advice I received from
www.tgfab.com and he has installed both types into beetles.
Steve Arndt