you need:
clocks
clock -> fusebox loom
dash brackets
speedo sensor for 020 gearbox, MK3 Golfs are a great source for these
If its a 90 spec MK2 its easy as pie, dash loom is totally seperate. If it aint, can be a paion as the dash loom is very integrated into the car loom. Plus if one is 90 spec and the other isn't makes it a pain cos you gotta splice it all in!