IMHO, there is only one course of action.

1. Find a Subaru engine, whether of the 2.2 or 2.5 variety.

2. Buy any one of the few swap kits out there (smallcar comes
immediately to mind for one).

3. Install said kit / engine.

4. Enjoy a great increase in power and economy while maintaining all
the cargo space the van permits.

O:-)

sudhir