First, welcome to the forum, wyrwulf69!
What you should do is get a repair manual, about 17 bucks, then get a digital or analog voltmeter 15-90 bucks. THEN take out the instrument cluster and test if the guage is getting power. If not, fix that first. A gas guage measures the resistance from the float to a ground (frame), and diplays it. The 12v switched power gives the needle the power to move. Next, find the wires for your gauge in the harness- there should be 2 (the power is a 'common' power for a few of the instruments. One wire is the signal, the other, a ground. Test the resistance. Autometer.com has the specs for Fors under the gas gauge section. Different years give different values. If that's not in the correct range, the sender's bad or you have a broken sinal or ground wire. Check all the wires out first. NOW if everything's good to go so far, It's time to drop the tank, the repair manual will help there. My sender was bad in my '85, but the Ford dealer was able order a new one for about 40 bucks. Put the sender in, the manual should be able to help there too. Just keep in mind, this is a GENERAL outline of what I had to do... Good luck and I hope that helps!
Also, 33's will need a lift (body or suspention) or they'll rub. I THINK 4" is what is required for a sus. lift
