All i know is that they are much bigger than a 901 box. There was a pretty detailed article on a silver oval in Volksworld about a guy that did the swap. Mag was a while back, but worth finding/ that car is the baddest VW on the face of the earth.
If I remember right, it was a turbo'd type 4.
Damn, now I want to find that issue again, I'll let you know what month if i can find it(a friend had it)