[Hozer 88GTConv]

The thing is that it is probably your sending unit in the tank that is bad in the first place so a new gauge won't help you unless you are sure it's not the unit.
I just say this b/c the sending units are notorious in Fords. I have changed mine twice.
The unit is not so bad, but the connector that sits on top of the tank is pathetic and becomes brittle and falls apart over time.
Once the ground goes out on the connector, forget it.
I ended up rewiring the harness at the connector and haven't had a problem since.
Good luck.