While we're on the subject of adding center seats to your Westfalia...
I have a 2-person center bench seat for sale from an '85 Vanagon (the type
where the seatback folds down), that could be used in a Vanagon or Westy. 
Sort of a tan velour color (similar to the Westy interior color from the
era).  In good shape except that one or both armrests are broken off. 
Price: $100.  
Also, I have a rear sofabed with mattress (from same weekender Vanagon), if
anyone would like to replace the rear seat in their Vanagon with a sofabed.
 Located in Phila/Allentown, Pa., not practical to ship.  
-Ron Salmon
 The Bus Depot