1985 ford f150 5.8 dual fuel tanks-fuel gauge

i just purchased this one owner pickup that’s parked 4 years. replaced battery,primed carburetor, fired right up! find fuel leak at carburetor,fixed,fuel gauge show front tank empty,rear tank about 16th.put 5 gallons of fuel to front tank, no change. varnish smell while running went away after putting $10.00 of gas in each tank.front tank show empty, rear tank after several minutes shows 1/2 tank.switch to front tank and goes to empty with $10.00 of gas. front tank started a hash mark above empty now sows empty.is float bad? ground? test drove truck, small hill truck dies,level truck fires right up [before $10.00 per tank added].whats the common failure.cannot find any help on YouTube directly for 1985 FORD F 150 5.8 2WD! ordered repair manual. its running great, i have no help with repairs labor wise because we just moved and doing all the work.WHO’S ON FIRST I DON’T KNOW ON’S SECOND.very limited window for labor help to either drop/lower tank oGETS r remove bed. PLEASE I NEED HELP TO FIX FUEL GAUGE ISSUE SO I CAN GET MY CAR BACK AND SON GET’S PICK UP