Not sure what year your van is, but Iíve been looking for an upgrade for my 06 vinyl buckets for a while.
Lots of guys over on ExpoPortal like the Sienna take-outs you can find on EBay. They can also get pricey if you go for leather and add a set of swivels from BaseFab (MG metalworks/Expo vans). To the best of my knowledge they wonít work with the SMB swivels. BaseFab sells fixed bases as well.
What I opted for was to keep my eyes open for a set of 09+ fronts from any E-series van. They are the newer captain style chairs. I ended up scoring a pair out of an 11í E150 from the salvage yard a few weeks ago. Paid $160 for the pair. The bolstering is a little blown out and the fabric has a few small rips, but ultimately my plan is to have them reupholstered in leather, fix up the foam and add seat heaters. I figure Iíll be all in for under $1000 for the pair, and I get to keep my swivels. All Ford OEM stuff as well, which is a nice bonus.