There was some chat about the Subaru swap in the vanagon-subie group about a month ago but it was canned.
Try the Samba group. Name escapes me at the moment...

-Sean G

    On Tuesday, January 2, 2018, 12:16:39 PM MST, John Rodgers <jrodgers113@GMAIL.COM> wrote:  Planning on swapping the Vanagon 4 speed tranny for the Subaru 5 speed
eventually. What has to be done to the tranny to accomplish this! Also, can
positraction be added. It's a whole new thing to me!!

Anyone interested in a near new (less than 5000 miles since rebuild))
Vanagon Tranny (from my '88 GL) with late DIESEL diesel starter conversion?
No more failed rebuilt Bosch starters!

John R