Doing this at the minute, but haven't got that far, stripping down the 1.8t loom is a right ballache.
Mine is a 1.3 model, which comes with some of the bits you already need.
I'm going mk3 subframe and rear beam as wont fit on 1.3 subframe, using a mk3 16v gearbox & driveshafts, hydro-cable clutch using the Seat actuator.
You can use the 02j box and buy some 100mm output flanges, although need different driveshafts *heard* they are mk1 caddy items.
Brakes are being used from the 16v mk3 too although probably using the mk4 rear calipers.
All what I have heard, but got some people around that know what they are doing
