Electronic Distributor

I initially   bought a Mk1 variation as a GT carb engine. Over the years I replaced the 1.6 engine with a 1.8 but used the original distributor from the 1.6 .Recently the cap and rotor arm need replacing. So this is my problem I'd rather change the complete distributor. Scouring around I have come to think that there is a different unit for a 1.8 as apposed to the 1.6 variant I had fitted. So is there a difference?
My wiper motor only works at high speed and when I ordered one from VW heritage it was the wrong one and they wouldn't allow me a refund. So again is there more than one variant for my Mk1 Hatch. This GT was from South Africa and externally it is exactly the same as the GTi stripped seats and all 

If you can provide the engine number and the VIN number, that would help identify the correct parts