I have had a couple of 8v's and the gearboxes were more than adequate for the car, although 5th gear was a bit of a screamer gear. So I changed the 5th gear for that from a CL 4E box. This decreased the revs from 4000 @ 75mph, down to 3200. So I still had GTI performance, but a nice cruising 5th.
A friend of mine had the same car, but changed the gearbox for that fitted to the older Seat Toledo. Made the car too docile and it lost its GTI zing.