I went with a 1.9TD to replace my 1.9 wasserboxer after 243k miles.

This is a summation of my opinions of the options if you have to pay
someone else for an engine conversion:

1. Fix the existing wasserboxer - Replace the engine the first time
the repair costs you more than $100 - $200.

2. Replace with yet another wasserboxer - Really bad idea.

3. diesel
    - need VW diesel carrier bars and other off-the-shelf VW
connection/engine pieces
    - need to change gearing on transmission unless you have a syncro
running giant tires or don't like going fast (65 MPH).
    - expensive beautiful thing - reliable and low fuel consumption

4. Subaru
    - need special carrier bars
    - need special adaptor plate
    - reliable and powerful - can be expensive due to custom parts

5. VW 4 cylinder in-line
    - need VW diesel carrier bars and other off-the-shelf VW
connection/engine pieces
    - reliable and good mileage - install and maintenance can be very
cheap

Dana
85 Westy 1.9TD
2004 Beetle TDI PD 6 speed DSG