Got the rear calipers off the car.

They are a real mess, so I am looking at a new/recondioned set, rather than reconditioning the old.

But it seems like G36 are hard to come by, whereas the newer G38 is everywhere, and dirt cheap as well.

I know that the G38 was fitted on newer/bigger cars, such as the 44, B4 and C4 models, but will if fit my 1987 2.2 GT as well?

On the pics they look very much alike, so suspect only piston diameter is the difference, but would hate to get something wrong

G36, at app. 320 US for two inc 4 pads

<img src="http://media.thg.dk/DAT/pic/l/517066866710.JPG">

G38, at app 110 US piece, no pads included.

<img src="http://i21.ebayimg.com/03/i/000/c0/5b/a243_1.JPG">

The upper picture in your post shows the correct FWD calipers with fore/aft cable position.
THe lower pic shows a quattro caliper with right/left cable position.
As long as the e-brake position is the same the calipers should interchange i.e. the carrier spacing is the same.

Try looking for FWD Audi calipers from 90/100, they should interchange, as well as VW GTI MK II, those should be the same as well.

Hope this helps