Try these people:
http://www.rodshop.com.au/old-site/transmissions.htm
In my opinion, the best, most common trans to swap is the Borg-Warner T-5 model. They will give you an overdrive gear, are cheap, plentiful and strong enough for your engine.
You will have to work out what bolt pattern you can get an adapter for, then buy a T5 from the appropriate model. You may have to get a custom adapter, too.
It came in bolt patterns to match the small block Ford (302), Cologne V6 and 2300 cc 4 cyl engines (all in Mustangs).
It also was built in versions to match the small block Chevy engines, the 60 degree V6 engine family (2.8V6) and the 4 cyl (2.5 liter engines). These transmissions were placed in Camaro/Firebirds and compact pick up trucks.
Does your van have a shifter on the column? Most transmissions will not adapt to a column shift linkage. You will have to cut a hole in the floor and use the factory stick. You may have to make a shift lever with a funky dog-leg bend because the T-5 shifter will be a bit further back than what you are used to.