pretty much all interior wiring looms are the same, difference is the model year. From 1990 the looms completly changed! Also on pre-90 MK2s the clock loom has extra wires to the engine bay for the MFA functions, post 90 the clock loom is the same and you got extra wires in the engine bay looms.
Also the central locking and fuel pump looms run inside the main loom to the rear of the car, so you need to get that bit to match yours. However, if you have a 16v, an 8v GTI loom will be identical, except it will be missing the ISV controller loom. As long as this is undamaged you'll be able to splice this in without much difficulty.