Hubs/Brakes
Initially i was going to run a 312mm set up (that was fitted to the wife's tdi estate), however this limits my wheel choice and having spoken to a few people on the subject, they would be far bigger than necessary.
With this in mind i have gone for a 288mm set up off a vr6 (thanks to gary forrest)
5 stud mk3's have a different ball joint set up to 4 stud cars (incl mk2) so you cant bolt the hubs onto the bottom arms. Thankfully the arms are interchangeable though.
The arms that came off the mk2 were polly bushed and we managed to press these out and into the mk3 arms. With the arms bolted in place the hub can be bolted to it. From here you have options. To keep it 4 stud the centre part of the hub can be pressed out, new bearings in then use the centre from your original hubs. you'll then need to source 4 stud 288mm discs though. I was happy to run 5 stud though so fitted up the hubs as per stock. Doing this also gives you 14mm wheel bolts.
Mk3 vr6 flexi hoses are then needed to plumb the calipers in.
The next issue is the steering arms. mk2 and 3 track rod ends are the same part number so are interchangeable but the rack ends are longer in the mk2 so these need swapping over too, otherwise the wheels will be pointing in opposite directions.
edit, mk 2 and 3 struts are interchangeable too so they bolt up to the hubs as normal.
further edit, rear brakes.
To match the front end it would be normal to install a mk3 rear axle, this will give a wider track and a 5 stud brake set up.
I have cheated and just fitted mk3 gti rear discs (wheel bearing part numbers are the same so they are a direct fit). The wheels i am using are 8.5" on the rear so i need all the room i can get, hence sticking with narrow track, for now at least.
