The passenger seat has a fixed base. I assume this is not normal. Where can I get and adjustable one and preferably one that swivels so the seat can turn to the back of the van?

 

What year is your van? Conversion van?

 

Yes conversion van 1995

 

All bets are off then..... Conversion companies put all sorts of stuff in those. You *might* be able to find a stock seat mount, that has the adjustment, and swap your seat onto it, but, that depends on what your current mount looks like.