I did this to a 80 quattro, fitted a 1.6td from a golf gtd, it originaly had a 1.8 petrol so the gear box fitted. Ran it on veg oil for a few years cos Im a peece loving cheep skate hippy type
As far a gear ratio goes it was great for towing and maxed out at 105mph so not too bad
I was going to do a similar covertion with a 2.2 coupe and fit the 2.5td engine from a vw transporter.
The lazy solution would be fit massive tyres to componsate for the higher gear ratio.
