Upgrade gearbox to type r
 

I have a 1997 subaru impreza turbo awd UK 2000 and would like to know if the type r gearbox will fit if I change the diff and dash clock's

You will need gearbox, rear diff, potentially shafts / hubs depending on what gearbox/diff you manage to source (early R160 DCCD or R180). You'll need the DCCD Control Unit and also the thumb wheel as well for adjustment otherwise it will always run in AUTO mode which is 37F 63R bias. Whilst the clocks arent essential, for it all to work its the only way you'll see visually where your bias is set after using the thumb wheel. And dont forget 75w90 oils for filling the gearbox/diff too.