['68OrangeSunshine]

So you may have let the pro off the hook. You might still ask him what he thinks.
I took my drivers ed in '63 Impalas, donated to the school by the local Chevy dealer. I would guess they also have a 20 gallon tank. Fill the tank and see if that frees your float.
If not, and you have 4 jerry cans and a siphon pump you could empty your tank, drop it from the frame and pull the sender to see what's up. Use a brass bar and strike it off with a neon orange dead-blow hammer for no-spark security.
Don't smoke while extracting the sending unit.
If the float is saturated replace it. Look inside to see if the action isn't catching on some internal baffle. Truck tanks don't have them, but I'm unfamilar with sedans.