Thanks for the responses, not quite sure how long it will take to carry out. One thing I didn’t mention though was that the mk1 is an auto and the mk2 a manual. Hopefully won’t complicate things too much
Not a massive change , if it’s a mk2 engine going in an early mk1 car that was a 2 bolt engine you need to change a bit of wiring however if it was a 4 bolt engined mk1 car it will be plug and play
Difference was 4 bolt has the sensors by the crank and the 2 bolt has the cas at the side of the head
You would need to change the gear selector cables though if yours is a 6 speed
Craig 
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Dont even need to do that
The MK2 engine has all the holes on the heads to allow MK1 electrics to be just bolted on and away you go