Transmission and Linkage
When I began my project I figured I would need to rebuild the 5speed on the Eurovan and get new gearing to make it compatible with the TDI engine. That is actually the route I went, using Dave Fouts Transmission in L.A. Amazing guy and tremendous workmanship - races off road buggies and some drag racers as well. I had him put in a new 4.23 Ring and Pinion set that I found online to gear up the entire transmission, then had him swap in the 3rd and 4th gears from the Passat transmission. I ordered a .658 5th gear and had him put that on as well, to help bring the final rpms at 70 to 2650 or so. The cost of all this was about $2500, most of it for the many new VW parts that Dave put into rebuilding the transmission. So I now have a basically new transmission.

After beginning this rebuild I discovered there was a cheaper, easier way. Frans at
Dutch Auto Parts in Holland can ship a completely rebuilt EWB tranny, used by the non-TDI Eurovan/T4 diesels, along with any other parts you need, for a very good price. I ended up going ahead and getting a EWB transmission from him (for my next conversion : > ) along with all the other parts I needed to complete the conversion.

This was the gearing I ended up with in my rebuilt 5 speed. It's worked out well.
4.23 Ring and Pinion gear
1st 3.778 (from Eurovan)
2nd 2.118 (from Eurovan)
3rd   1.36 (from Passat)
4th   .97 (from Passat)
5th   .658 (from one-stop-gearbox-shop, or Bora Parts).

Because the 5th gear is outside the regular transmission on all models of this generation VW the 5th gear swap is a relatively easy thing to do at any point.
Here's a good write up:

If you are doing a swap from an auto to a 5 speed you will need the linkage, shifter and boot, clutch pedal, clutch hydraulics, and right and left axle shafts for the 5 speed transmission. I'm not sure if you need a new brake reservoir from a 5 speed since the clutch reservoir feeds off the brake reservoir, so there may not be a hole for the clutch-line in the reservoir for automatics.

The Linkage bushing wear out on the Eurovan 5 speeds. Since it had broken on my in the drive over from Florida, I ended up pulling out the entire linkage out of my Eurovan and rebuilding all the pieces, buying all the new plastic bushings from Europarts-SD.

Here's a good thread of replacing various linkage parts: