What do i need to make it fit?
Do they share the same diff rarios or do i need to change the rear diff to the R180 version as well?

Thanks

 

you'll need a rear R180 4.44 conversion.
Or if you can find one an R160 4.44 rare as rocking horse **** though but will save you swapping everything.

 

I've got a full dccd conversion done on my 1999 uk classic turbo, I've got a version 4 dccd gearbox and a R160 4.444 rear diff, version 6 sti ra dccd loom, dccd controller and thumb wheel and version 5 dccd clocks