Not wanting to sound like im teaching your granny to suck eggs but were you aware that in europe we got the T3 (Vanagon) with a 1.6TD installed.
I run a small garage in the UK specialising in the T3 and I would say 30% of my customers drive 1.6TD T3's.
You can make this conversion totally bolt together, infact today we have just returned from a VW show where the guy I shared the stall with (
www.syncrospares.co.uk) sold a complete T3 TD conversion kit.
The engine code you are interested in is th JX
Things that differ from the 1.6D or 1.7D
You will need a spigot shaft bearing in the end of the crank if using a Golf etc motor.
JX exhaust manifold, same as Audi 80 having it's exit by number 4 exhaust port.
JX sump has drilling for oil return line from turbo.
JX has an electrical auxilliary water pump
JX downpipe and back box are bigger dia and different design to other Diesel engines.
T3 215mm flywheel.
The Diesel bellhousing is different to the petrol one, starter also.
Injection pump top is different, it has the LDA laid on it's side as not to protrude through the engine lid.
Well, I've had a few beers and thats what I can think of!
If you need any help then give us a nod.
Check this brochure, you can see a picture of the JX and the exhaust
http://vwpix.terlinden.com/prospekte/deutschland/grossraumlimousinen/Caravelle/1990_01_Der_Volkswagen_Caravelle/index.html