I have a B5.5 4Mo wagon, AWM engine, but it is an automatic. I harvested the entire driveline and everything needed to make it run from a wrecked BHW car. I looked into converting it, and here was the problem I ran into:
The transmission.
So, both the BHW and AWM engines bolt to essentially the same 5HP19FL ZF transmission, the 4Mo cars use the FLA (Forward mounted Longitudinal All wheel drive). The issue is the gearing. The BHW uses a substantially taller geared transmission. I do not know if it is JUST the final drive or if the actual gear ratios are also different.
Since my AWM's automatic was working fine, I was content to just at least for now use the lower gearing with the diesel. The AWM automatic is geared fairly close to a 5sp ALH car (at least the top end is anyway). However, the TCM's shift mapping is also all wrong, so even if I bolted the BHW up to the AWM's transmission, the TCM would have it spinning the engine WAY too fast and downshifting/holding gears much too different (the AWM will happily spin past 6000 RPMs, and if you stab it doing 70 MPH, it will jump down to 3rd gear!).
This problem *could* be fixed easily with software. All I'd need to do is program in the AWM transmission ratios but use the BHW transmission shift mapping, or at least some happy combination of the two. I could never find anyone to do that, although there are people that do this for Porsches, and they (Boxster) use essentially the same ZF transmission and same basic TCM. But trying to get the Porsche elitists to do something for us diesel Volkswagen peons is next to impossible. Pricks.
So, next obvious choice would be to convert the car to a manual. Manuals don't care about any of that crap, because all that is done via good ol' human gray matter.... but, the REAR differential would also need to be changed, because for reasons unknown to me, all the manual 4Mo B5s use one ratio rear diff, all the automatics use another. I'd rather have a manual anyway.
So.... not many stateside donors available (obviously these would all be gassers). The B5, while based on the same chassis as the Audi A4, uses the same REAR suspension as the larger Audi A6 (we are talking AWD cars here.... the FWD is completely different). So while they sold plenty of quattro stick shift A4s here, those won't help for anything beyond the transmission itself. Rear diff and prop shaft won't work. And I could probably count on one hand how many manual A6 quattros that Audi sold here.
So that left importing transmission/rear diff.... and Frans was never able to get back with me.
So, I gave up, fixed the AWM (it needed its breather box rebuilt, its SAI deleted, and a couple other minor things), and it still motors on... recently crossed 1/4 million miles.... 23 MPG on Premium and all (thankfully I don't drive it much). But if mine were a manual, I'd have already converted it.