I'm not sure on the caliper/carrier combination, and IIRC the alloy mk4 calipers might not fit inside all 14" wheels? Would need confirming.
Personally, I don't think a car as light as the G40 really needs better rear brakes - front's yes.
The biggest problem with the standard drums is keeping them properly and optimumly (does that word even exist?
) adjusted. I have found that even after fucking about manually adjusting them up, that within a few hundred miles the brake pedal has gone "long" again. I'm convinced this is why 99% of people complain of shit brakes on the mk3 Polo's. The actual physical size of the mechanical parts/swept area is more than enough for such a light car, it's the back brakes inability to keep fully adjusted that let the system down in terms of pedal feel and travel.
Fitting rear discs will give you more "efficient" brakes and apparently the handbrake is far better too. However, you won't reduce your stopping distances because they would just lock the rear wheels if they worked any harder than the standard drums.
To get the very best out of them though you need to get rid of the O.E. master cylinder/servo setup and the rear load bias adjuster shite. Then you can fit an adjustable bias pedal box with individual correctly sized master cylinders, and suitably upgraded front brakes too ie; Willwood 4 pots/260mm dia. discs. Very expensive and lots of work, but the proper way of fitting rear discs IMO.
However, you can use a bigger Passat 22.2mm master cylinder if you're a cheapskate!
