Fuel tanks haven't been gravity fed since the 30's, I believe. You have a mechanical fuel pump, yes it will pull from a tank between the rear frame rails.
The sender in the camaro tank won't work with your stock gauge. The gauge works on a 0-30 ohm sender, the camaro is a 0-90 ohm sender. Putting a 60 ohm resistor in-line will not work. Best thing to do is to adapt a sender from the same era as your truck to the camaro tank.
