I think that the drive shafts are different sizes unfortunately. The diameter of the end of the shaft that joins to the gearbox is 100mm on GTi's and 90mm on selected diesels and drivers.
Thats what you'll have to measure.
http://www.scirocco.org/gears/Try the above for the gearbox codes, and what size flange they have, although that particular site doesn't give the engines codes to match to the box. So on your trip to your scrappy you need to checc the box code which is located on the bell housing of the box.
Good luck
