Hello there.
Im sorry to bring this old thread back again, but I found this on eBay:
Its claims to be for 1998-2003 Rangers.
I have an a/c evaporator plenum box in my garage. After I searched for it I compared to the one in the image, and they are identical (except for the evaporator core tubings and vent resistor). The plastic assy is exactly the same and this one clearly shows an cabin filter fitted.
The seller claims to be 100% original Ford.
I guess a couple of us wont sleep today searching for an answer!!!!