See this part of the post you quoted.

"floor tracks that can be fitted to any year van using the threaded
holes always present in the floor"

Mark

Dave Mcneely wrote:
>>>
>>> You can install a single person center seat that was optional in just a
>>> few years 85/86, sliding onto standard floor tracks that can be fitted
>>> to any year van using the threaded holes always present in the floor.
>>> These have a lockable storage compartment in the front of the base and a
>>> small open area in the rear of the base. These also swivel 360 degrees.
>>> The seatbelts attach to the base and the whole setup can be taken in and
>>> out at will, though it is heavy. These came in tan fabric only but any
>>> Vanagon front seat will slide onto the metal base/swivel section. I just
>>> put one of these in my pass van a few days ago.
>>>
>
> Is this installation possible with a '91 camper?
>
> Thanks, mcneely
>