The faceplate on the gauge was installed backwards?
(sorry I couldn't help it)
I'm guessing the sender and gauge aren't the same brand, or from the same seller ???
If they are, ask them. If they aren't you may need to change either the sender or gauge to match the other.
Is there a chance the wiring connections on the gauge got accidentally reversed?
Double check it's installation instructions. Depending on the source / mfr of the gauge it may make a difference.
I won't suggest reversing the gauge connections 'Just to see what happens'... yes it could be worse. (then you would
have to buy a new one)
Another stray thought... I've been told when Ford upgraded their dash gauge design for cars in '57 it reversed the way low / high elect flow affected the internal gauge parts. Ford may or may not have done the same change for trucks that year, maybe the year after. It might be possible you were accidentally sent parts for the wrong year. Or that particular supplier may only have generic replacements that don't take everything into account.
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