Idler Pulley Assembly

1999 Mountaineer
Can anyone tell me if the following parts are the same, i.e go into the exact same location?
F7CZ-6C348-AA F8CZ-6C348-AA
These are idler pulley assemblies for a '99 8 cyl Mountaineer. I had the F7 part replaced, then at later date the F8 part replaced and dealer states one was the upper assembly (F7), and F8 was the lower. Therefore I had to pay for the latter repair, as they claim they were different repairs. I believe that the F8 is just an improved updated replacement for F7. Other dealers have told me there is only 1 idler pulley assembly. Both repairs were performed to correct a continual squealing noise by the belt drive.
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