Did the 1982 Ur quattro have a brake servo or are you talking about the power unit that is behind the brake master cylinder that has power steering fluid passing through it, part number 1 in the image below, LHD 857612107A 07/80 to 07/87 or RHD 857612107B 05/84 to 07/87, you may well be looking for the LHD part due to the early cars being LHD or LHD shells converted to RHD but all Ur quattro have the brake master cylinder in front of the passenger in
all RHD cars.
http://www.oemepc.com/files/img/Bild.../046052000.png