80 El Camino Fuel Guage

I bought this car just a couple weeks ago. Needs floor pans replaced. no biggie. what I need help with is why was the fuel gauge working until i filled it up...now it's stuck on full. I checked fuses all are good. Also dash lights have a short so not sure if they are one in the same problem or not. Any help would be appreciated!!!!

is it possible the float in the tank is stuck??