Winkler in Herne, Germany, offers slotted 14" rotors and a conversion
kit to a four disk brake system (front will be 15" air vented). The
conversion kit is also available from Oettinger who has a subsidiary
in US. 15" air vented front brakes for Vanagons are also available
from VW South Africa, but I don't know if they will fit the pre '92.

Helmut
'80 Camper