Most vans came with the 727. Did you look at the pan? I don't have a resource to look the numbers up. I have seen 904s in vans but VERY few.......and that means nothing, actually. LOL
I have noticed that on A&A transmissions catalog they have a 904
Tail shaft that they sell that was apparently used on vans. That tail shaft is much more heavy duty with substantial ribs versus the stock one.