This sounds like fun.
The 02A/02J series all-wheel-drive gearbox is the 02C.
The 02C dates back to the 1990 g60 Passat in North America, and was still used in the mk4 era, with some minor changes for the new motor mounts.
The syncro AWD system from the 90's is passive, vs the active haldex from 10 years later.
It is possible to use the early 02C with the haldex, but the angle drive is a different ratio in the mk4 models.
The 02A has factory mounts for the mk2 from either the B3/B4 Passat or the Corrado, same for the hydro clutch.
The AWD needs a higher center tunnel, the higher tunnel was used on the B3/B4 Passat wagon, the B3 Passat syncro, corrados, and mk3's.
The 02M has been swapped into the mk2 enough times now that you can buy the swap parts and there are detailed walkthru's on the interweb on moving one of the transmission mounts on the subframe.
The 5spd 02M in the 180hp TT Quattro (DXW code) uses the same gearset as the TDI DRW code, but with different output shaft ratios, and is missing 6th gear. 6th gear from a DRW can be added to the DXW with very little work. You only need to add 1 cog, not a gearset.
Assuming 205/50/15 tires and a 4500rpm redline, the DXW with 6th would top out at 115mph. 70mph would be ~2725 rpm. Pretty high if you're looking for economy.
The DRW front wheel drive gears and shafts can be swapped into the 6spd quattro gearbox with zero issues, it's just a matter of swapping ring gears on the diff and changing the case.
Similarly, if you find a gasser 02C transmission, the 02J gearset can be swapped in.
The 02C and/or the 02M transmissions with the angle drive fit the ALH TDI with zero issues and there is no conflict with the turbo.
Here's a close up of an 02C on an ALH with a VNT15. Fits with a VNT 17/22 just as easily. It looks like the driveshaft would hit the vacuum actuator. It doesn't.
For your mk2 you'll probably need to build a custom downpipe, but factory parts are available for a downpipe on the mk4 chassis.
Nice aftermarket stuff too like this:
Darkside Developments in the UK
Operating the Haldex on a mk2 TDI swap is pretty simple with the Touch Motion from HPA. You don't need to worry about complicated wiring or functional ABS or any of that.
Everything, however, has a cost, and it all adds up.
Making a mk2 AWD is not an inexpensive task, unless you already have all of the parts.
One thing you can do for now, meaning you can get things running and driving, it's ok for the output from the angle drive just to free spin wihout a propshaft attached, meaning the AWD trans can be installed and you can install the rear end later.
My mk4 ALH TDI currently has a hybrid transmission in it:
02J gearset from the TDI (EBJ code, I think ~3.4 final)
02C case (CBC code) with angle drive from '92 Passat
6spd add on from EuroTuning
The angle drive output is currently free spinning.
The ALH has a VNT 17/22 and I have Darkside's downpipe.
I also have an angle drive from a mk4 with the correct ratios for the haldex, so I currently have the options
of installing a syncro or a haldex system.
And in a past life I built a syncro Corrado, and added the 6th gear cog to a 5spd Audi TT 180q.
The 180q also has the Touch Motion.
My ALH into mk1 swap was many many years ago.
-Dave