Actually the OBD2 wiring harnesses are easier to modify for Vanagon use than the OBD1 2.2 harnesses (ask anyone who has done it)

2.2 non-interference is a plus.... but as long as you change the timing belt at the required interval you should not have a problem with 2.5's, and Subaru sells a "California" timing belt good for 110k miles so you don't have to do it very often.

Finally "low mileage" JDM engines are a bit of a scam...many of the ones sold by the importers have many more miles (or problems) than stated...and there is no way to verify true mileage since you cannot "carfax" a JDM engine.   I've seen "30k mile" JDM engines that burn oil like they have 200k on them....bottom line, YMMV/buyer beware with JDM engines...