[redmodelt]

The center and back seat didn't use rails, there should be a number of small plates set into the floor with more or less square holes in them. The seats had stand offs, the front ones were a kinda hook and the back ones were kinda arrow shaped. The front pair went in to the first row of plates and allowed the seat to be rotated back, the rear arrow shaped ones went into the 2ed row of holes. Those had a spring loaded catch that held the seat post in place. The seats have some brackets inside under the upholstery that supported the back.

Up to about 4 or 5 years ago you could buy the parts to install the two rows of seats but are no longer being made. I think there was someone that was going to take over making the parts but don't think it went anywhere.

If the plates with holes are not there I think you will have to get creative. Can you post a photo or two of the floor?