Very few 15" Mercedes stock wheels will fit the 2 WD Vanagons without
spacers and longer studs. The easy ones to find are the wrong offset.
Cheap used 190E and 300E wheels are common but not the right choice. You
need an offset of about ET23 for a 7" rim or ET30 for a 6.5" or ET37 for
6". The more common Mercedes wheels are between ET45 and ET50 and these
will rub with many tires. Mercedes wheels do not need the centers
machined but they do need the lug bolt holes enlarged by 2mm. The
Mercedes has 12mm lugs and the Vanagon uses 14mm.

Syncros have more clearance up front and many more Mercedes wheels will
fit them without rubbing.
I was once working on a list of Mercedes wheel part numbers and their
specs but I have put it aside for now.
Look for part numbers beginning with 126 as these are likely to have the
offsets needed for 2WD models.
All stock VW, Audi, and Mercedes wheels I have seen had the ET# and size
info stamped into them.

Mark