‘96 F150 - gas gauge reads past full

I know there’s gotta be someone on here that has worked on a dual tank F150 fuel system, seems like it’s a common thing to repair.

I bought an F150 and only the rear tank ‘works‘. The guy I bought it from says he ‘disconnected’ the front tank. I’ve been driving it for a few months. I just confirmed that there’s no gas in the front tank, so it doesn’t appear that the rear tank is draining into the front tank which allegedly sometimes happens.

I’m totally fine driving around with just the rear tank - the problem is the gas gauge constantly reads past full. When I first got the truck, the tank would be empty when it displayed a half a tank on the gas gauge - but now it generally reads full all the time, and the tank is empty when the gauge barely drops down from F. So it’s getting worse and trending towards showing full all the time. The digital trip-odometer display is also burnt out, so I really have no way of knowing how much gas is in the truck.

Does anyone know why this could be or how I could fix it? 🔮I’m calling upon the communal knowledge of the Internet.

Thanks squad