The TDI conversion is an excellent idea.  A couple of the problems with it
right now are:
1. Price of used engines is usually around $3500 complete
2. Availability (hard to find)
As time goes on both of these will get better I am sure.
We are selling a TDI conversion kit for $2300.  If you are interested in it
please pmail me and I'll let you know what it contains.  It has been setup by
Winkler and has been sucessfully used in Germany for several years.
Of course there is always the 5-cylinder conversion which is simpler and
cheaper, but I digress...
Ken Wilford
Van-Again
John 3:16