I'm going to a pick n pull tomorrow for a trans for my 91 2wd. Their online inventory only shows one 2wd F150 in my year range with an auto, but shows at least 12 E-series vans with auto. I know for a fact that my truck is an E4OD with the trans code 'E' on door jamb sticker and the OD cancel button on dash. Anything the same year should be compatible as long as it same engine/trans right? Since of those 12 there is at least 5 that are 91's.

I had a line on one at a non pick n pull yard but it turned out to be a 4x4 trans, plus that would have costed $400+tax and the pick n pull is $90...

 

They can give you the interchange at the yard, but pretty sure it's the same.