I found this # parts

Serpentine Belt Idler Pulley (Upper, no grooves)
(Ford) F6TZ-8678-GB
(Motorcraft) YS-267
(Napa) 38052
(Autozone) 231057
Serpentine Idler Pulley (7-rib 94 only)
(Ford) F5TZ-8678-A

Serpentine Belt Idler Pulley (Lower Grooved, 8 rib)
(Ford) F6TZ-8678-HB
(Motorcraft) YS-268
(Autozone) 231048

 

Last night I took a picture of the two pulleys and the part numbers on the boxes so I can send it to Horizon Ford if I need to.

The part numbers are exactly the same on both boxes. On the bottom of each part label there are three sets of numbers; the set on the left is the same on both, the set on the right looks like a manufacture date, but I can't determine what the set in the middle might be, and those are different between the two boxes. The picture is below:

 

Hopefully we can get some sort of answer as to why this happened.

 

So thats the correct # part, BUT (moral) you have to check what its inside the box to be sure is the RIGHT pulley, BEFORE you go home

Maybe someone knows about the middle low number. IDK.

Thats WEIRD.

 

The problem is that it's not exactly applicable if you order online or if the dealer or other vendor has to order the part. Also, these old trucks have quite a few updated parts that may or may not be identical in appearance to the old parts. It's sort of hard to tell until you fire up the truck with the part installed. You're right, though, in that it can never hurt to visually inspect parts before you buy them.

In this specific case, don't buy the pulley with the shields on it, or return it immediately if it has the shields. I guess you could theoretically modify it to make it work, but you shouldn't have to do that with a brand new Motorcraft part.