I believe 86 was the year of change to a larger engine, but I would STRONGLY recommend a different engine than stock, the stock engines are border line anemic, a 5500 lb van with 91 hp???? Lots of info on engine swaps, from fords to subaru to TDI's, and for a reason, not enough power!
Maybe the good side with keeping the original engine is most repairs can be done by more shops, most shops will not touch a VW with a different engine, but on that note, getting to know this vehicle will be in your best interest, and doing all or most repairs will be the only way to afford it, these are old cars and need constant attention, and if paying someone to do all the work you wont be going travelling. (I speak from experience ) Some thing I read some where and it worked for me, was to buy the newest and best condition van you can afford. Last year of the rear engine westies was 1991.