My tank is also from a 2005. I did have to shorten it 7" to fit between wheels and cab, so what was 80 gallons, is now almost 75.
The tank on your truck, can you inspect a few things for me? the straps that hold it on, what is the detail of washers and nuts on the end of the T-bolt? I have a SAE flat washer, and a regular nut. From the factory, was there a lock washer, or a second nut, or? The other end of the strap, with the pin, is there a flat washer on both ends of the pin, or just the end with the cotter pin, or the head end, or no washers? The fittings for the fuel suction and return, I have one 3/8" npt port, and one 1/2" npt port, which is used for suction, and which for return?
Another question, at what fuel level does it slosh around and suck air causing problems, nearly empty, or 1/4 full, or?