The pin-outs to both clusters are available so it should be possible to cross-wire things electrically... and since the 96 Jetta donor probably had an AAZ engine as well the tach will probably be OK... no difference in pulley sizes like there is when you go MK2 - MK3 from an engine perspective. You'll need to find a junkyard to grab a MK3 cluster pigtale.
The only hurtle that springs to mind is the speedo... the new cluster is expecting an electronic VSS signal to drive the speedo, while your 87 Vanagon probably used a cable drive to drive the original cluster.
If this was a standard car you could just yank the cable gear from the tranny and drop the electronic transducer in its place, but all of the vans I ever played with drove the speedo off the front wheel. If so you might need to find a mechanical drive converter (or kludge one up).