So, on your advice I ordered a new one and it arrived today (it is very nice and well made). The problem is that it appears to be incorrect although it is the part number from the Porsche parts catalog (same as in OP).
The cutout is on top and seems to be for the VR but is ~1/4in to short as are the slots for the studs. I am debating whether to return it or modify with a dremel (I lean towards modify as I am impatient).
Some pics with the original alternator (successfully replaced with one from Ebay (Eagle Elec))
