[FordeatinZ71]

first, WELCOME! secondly...the idle screw. if it's a factory QuadraJet carb, the idle screw is right in front of the throttle butterfly on the carb. just look where your throttle cable connects and look around that. you'll see a flathead screw with a spring on it...you'll see how it goes against the throttle shaft...just turn it counter clockwise to raise idle...and vice-versa to lower.

as for the gauge...it could be a few things. first, i'd try putting more fuel in it just to make sure you have enough to make it register. if you do...then you will need to check the gauge first, then the sending unit. it's easier like this because you have to drop the tank (or remove the bed) for the sending unit. IIRC you can ground out the wire for the gauge (on the sending unit) and it SHOULD make the gauge jump to full...if it doesn't, you have a bad wire/gauge. if it does...the sending unit is toast. i'm betting the sending unit just wore out. to replace it, you'll need to drop the tank/remove the bed (pick your poison), remove the fuel hoses on the sending unit, the one wire going to it, and remove the locking ring that holds it on (just turns off with the aid of a screwdriver and hammer)...then just pull it out and install the new one...