Now i've run into a second obstacle. The "anchor" receiver (small black receptacle on the door-side of the passenger-side seat) is on national backorder.
So even if the Transit receiver works for the main buckle, I still need to figure out how to source this "anchor' receptacle. At this point it would be easier just to swap out the seat belt assembly for the old-style (which I do actually have lying around). But it would kill me a little to have mis-matched seat belts (both style and color) in the van.