You have different clocks according the CE system.
CE1 has two plugs, One black, one white. Wiring colors are exactly the same as the big plug on the MK1 except the two oil pressure wires which you have to swap between them. yellow and black/blue. However, the black plug is going to hit the column support. You will will have to remove the plug and bent it so that it clears it.
Then its the CE2 1989 1/2+ clusters. These have one big white plug. The colors are different. I've created this guide which tells you exactly what to do.
http://forums.vwvortex.com/zerothread?id=1924586. You need to open the speedometer cable hole a bit and trim the top of the cluster housing to make it fit. Personally I tried both and the late 16V cluster suits me well.