I pulled the box out of my S3 to put synchromesh rings in it but on inspection 1st and R were badly chewed up so after advice from here I bought a full synchromesh box. Upon opening I found the input shaft bearing housing was cracked and the snap ring had come out and dislodged the synchromesh ring this was bad and good, good because it must have happened early in it's life as the rest of the box was in very good shape. With no luck finding a new housing I looked into having a new one made from steel, that became somewhat price inhibitive so I was stuck. I started looking at the housing of the S3 box and after extensive measuring the only difference I could fine was from the face of the housing to the end of the input shaft where the synchromesh cone ends was 1mm longer and the oil seal was 2mm wider in the housing. I made up a 1mm spacer to move the housing back and took the housing and input shaft to Canadian bearing and they matched up a seal and bearing, I had them pressed together and reassembled the box and put it back in. Well last weekend I did 100 miles in my Alpine and could not be more pleased, quiet smooth shifts and no leaks 
