if its going to have a 1.8t it makes no odd what mk2 you buy, the wiring is going to have to be spliced to the fusebox no matter what. if it was a mk3 engine you were going for then buying a 90spec mk2 would make it easier, but mk4 has totally different fusebox. a gti model would be a little easier though as the injection pumps, wiring and pipework are already there.