trouble with most 5x100 bearing carriers easily available is the offset on the balljoint is further forward/back, so the wheel isnt centred in the arch if you bolt em up to 4 stud wishbones. You can push 5 stud hubs into 4 stud bearing carriers but then you need to re-drill the discs.
Recently though someone on ed38 mentioned that a 91 passat 5 stud setup will work. Looking into it on ETKA they use the normal 4 stud hub carriers with a passat specific 5 stud hub and brake disc. I assume this disc would work when pressing a MK3 5stud hub into a 4 stud bearing carrier, but this I have not tried.
back to the op, you could swap your setup for an early MK3 280 setup without much trouble I bet, then sopurce a pair of passat 4 stud 256mm front hubs, again scene tax free
