[dsraven]

a hydraulic shop or a hose builder shop is also a great place to look for fittings/ you could have a custom hose built to connect to the fuel pump, where the barbed fitting is located, and then connect to the flared fitting on the steel line at the frame. then install the fuel filter at the outlet of the fuel tank where it is easier to change anyway and you can also use a drain pan on the floor to catch the drips. a fuel shut off on the tank is a great idea here as you can simply shut the supply off, remove the filter and not have an open hose draining the tank while you quickly try to get the old filter off the hose and a new filter installed. I guess you could also install a spin on fuel filter here if you really want overkill. lol.
another thing to remember is that the original fuel tank was in the cab, so it drained automatically to the fuel pump. if you have installed a fuel tank on the frame somewhere then that auto supply is not so good after the tank has drained down some so the level of the fuel in the tank where the pick up tube is located is about the same level, or lower than, the fuel pump inlet. the fuel pump then needs to draw the fuel up from the tank. then factor in when the truck goes up an incline and it gets worse (right when the engine usually requires more fuel). basically the pump in this situation needs to create a negative pressure and atmosheric pressure acting on the fuel in the tank pushes the fuel out to the fuel pump. I know, that sounds like baloney but thats how it works. anyway, that is why the inlet side of the pump is usually larger sized tubing or hose compared to the outlet side. just something to keep in mind with the hose and fittings.
keep us posted with your results or if you have questions and also what your plans are for the connection. a few pics wouldn't hurt either. nice clean build you have going there by the looks of the pics you have shown.