Rough estimate Ben:
- 4spd box - $600 to $800 from an EB to ED. Could get cheaper if you hunt really hard.
- Trannie fluid - for the full change of around 10.5 litres - approx $60.
- If going to use the secondary ECU that controlled the gearbox that was found on the EA II's and the EB I's - not sure but $50 to $100 ?? Other than that, fully integrated ECU - some buggers quoted me $150 to $200.
- Will need to make new mounting points on your car to fit the 4spd auto as well.
- Some rewiring as well, but not impossible.
- Internal plastics/trims
- Gear Selector handle (get rid of the old ugly one)
Also check the filter while you are there.
There maybe a few other things I am forgetting but I would say around $1000 plus. I would buy a wreck and pull the parts off of that - as you can use the other parts off of the car - great if you have a farm to store the wreck :) . Try and check the colour of the trannie fluid as well if you are going for something you do not know about. Not a guaranteed way of knowing what the box is like, but least you know they looked after it a little bit.