Gearbox 020 question

So I need to replace my gearbox and have checked the code from the gearbox (020). Now I needed to check the ratio. I have a 1.8 GTi 1986 cabriolet. Will any box fit or do I need the right ratio code or will it just fit. 

Sounds a bit of a stupid question but hey still need to know. 

Any will fit, may need to swap the drive shaft cups over if different size (later mk1)

All the info you ever need about gearboxes on this site
020 GEAR RATIOS

There should be some letters and numbers on the bottom of the gearbox so you can see whats fitted to your car, Ive got a ACD gearbox. (I should get a better picture where my engine is not covered in oil after a major oil leak from the oil cooler seal!)

apart from the flange size the other thing to look at is the reverse switch. early GTI have a large multi pin plug which works the analogue mpg gauge/shift light, later cars have a 2 pin switch and just the digital mpg gauge without shift light

Thanks for the answers, have a box arriving tomorrow. No just need to sort the idling running at 1500rpm and the constant loosing water and will be fine.