The only bus Ford made was basically an extended-body van, with an extra long rear extension. The lower body panels were the same as regular vans, but slab-sided above the belt line:
If your bus body does not have the stock van body lines, Ford only built the cutaway chassis.
4x4 was not offered by Ford. Around that time it could have been SalemKroger, Advanced, or Quigley. Or maybe even some school district's home-built conversion?
SalemKroger was based in Red Bluff, CA.
BTW - I think '89s came with the 6.9L?