I'm sure the answer to that one is, like just about anyone else
considering an engine swap, more power. If you aren't running AC in a
Vanagon, then the stock 90 hp is JUST barely adequate to cruise around
town. if you are using AC, then it isn't adequate at all.

For example today, I was 6th car in line at a traffic light. Light
turned green. Once the car in front of me starting moving so did I. I
stopped on the yellow light. That's right. I never made it to the
intersection before the light turned yellow. This was on flat terrain.
Throw in a few hills, and the lack of power become even more annoying.

I'm not sure how many horsepower the AC takes in a Vanagon, but I'd
guestimate it at around 20hp. That's a significant fraction of your
total when you only have 90.