Please Note, This information only relates to the Golf 2 Syncro as the 1.8 Golf 3 Syncro does not have the caliper carrier mounting lugs, only the Golf 3 VR6 has them.
As stated below the most fiddly part is grinder cutting off the old drum backplates, you can remove the hub instead but then you will need new wheel bearings, the necessary caliper carrier mounting holes are already drilled & tapped in the swing arm you just bolt the carrier to them and your away [
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Taken from here
http://www.vwsyncro.co.uk/data/forums/topic.asp?TOPIC_ID=119
Upgrade 2
Replace rear drums with 239×10 discs, this is not as quite as simple as upgrade 1, but it is without to many problems, the replacement disc part no 811 615 301, this is actually the same disc as fitted to the golf 2 1.05L front wheels!
The calipers are part no 535 615 423x left and 424x right and are the same as fitted to the rear on a gti 16v and most other vw rear disc applications of this era,
The caliper carriers are part nos 191 615 425a left and 426 right, and have been fitted to all car type rear disc syncros 1985 to 1998 thats golf, passat, vento and jetta, the awkward jobs on this conversion are cutting off the drum brake backplates, and lengthening the outer or shortening the inner handbrake cable, this is the rear disc conversion as fitted to my car.
My new conversion uses mk 4 aluminium calipers which are lighter & have a better(non seizing)handbrake mechanism
This may also help.
As may this
http://www2.plus8.net/jpegstore/uk/vwsyncro_chriss/archive/Technical%20info/fullres/dsc00565.jpg
