Yes, it will, but the small blue exciter lead in your van may have the wrong style of connector on it for the alternator you are trying to put in. Some alternators have a standard 1/4" spade connection, while others have a 6mm post, which requires a round connector. I just made a small pigtail for my van, with  both connectors on it, so whatever I get for an alternator, it can go right in. I plan for parking lot changes, with minimum tools, miles from home, you see...
The main thing to watch for though, is not the type of connector. It is the output of the alternator. If you are needing a 90 amp (fitted to later vans), and put in a 65 amp (earlier vans), there will be unhappiness in your neighborhood. There may not be enough alternator there to keep up with your needs, which can lead to low voltage issues - dead batteries, dim lights, odd running behaviors, radio not working right...  ...you get the idea.

robertmstewart <robertmstewart@MAC.COM> wrote:
  Does an alternator from a pre-86 vanagon work in post 86 vanagon?

--
Rob
NYC/Long Beach, NY
88 Wolfsburg, Silver