Sorry to resurrect an old thread but I thought it may be useful to fill people in on how I managed a double swivel passenger seat in our mk5.
As another poster mentioned, the Toyota Previa (1990's shape) comes with a double swivel in the rear. To fit it, I cut down a frame from the original double seat so I could use the orginal bolt holes, put a piece of box section at the front/back and finally welded the complete Previa seat onto this box section. The height from the ground to the top of the base of the seat is identical to the drivers seat. However, the back is quite low and lacking a headrest for the seat closest to the window so I had to make one up from the old Transit seat. The seat can do the full 180 turn (with a few cm's to spare), slides backwards and forwards and best of all, folds flat so can be used as a kids bed.
We find it great, it's amazing how much extra space it gives when it's facing the living section.

