how the FUEL SYSTEM electrical goodies connect ?

Nice clean truck. The tank selector controls on those are a very common problem. It switches power to each pump as well as each sending unit. It's also an easy place to test the pumps as it carries full power for each pump (which is why it tends to fail).
Power comes from one fuse through the pump relay and through the inertial switch. As yours runs on the front tank that all works. The power then hits the selector switch, it comes in on terminal 5 on the Red/yellow wire The sending unit for the gauge is on terminal 2 with a Yellow/white wire. The front tank power to the pump goes out on terminal 6 Red wire, while its sender is on terminal 3 (sounds like this side works) Switch to the rear tank and the power feeds out on terminal 4 Brown/white. You can also connect battery power to that to test the pump. The sender for the rear tank is on term 1. Now if you have no pump activity and feed battery power to the pump and still get nothing, does the rear sender work? If no then you could have no grounds at the pump assembly, there is a connector under the truck that both of those plug in to, Has one black wire and one orange wire, orange grounds the pump, black grounds the sender, then they both continue to a splice point that also carries the front tanks grounds, if that connector unplugs or corrodes, no ground to the pump or sender and you get no fuel. Basically each tank operates as it's own unit with the switch controlling it.
Line wise it depends on which line system you have. The common one just runs the pressure line from each pump up to a Y fitting and depends on the check valve in the pump to keep fuel from backflowing. The return lines work in a similar fashion. They did use a reversion valve on the later models that could be installed. It blocked flow independent of the internal check valves. On the later systems they used the selector similar to the diesels, that has solenoids in it that switch when you select each tank and isolates the tank that is off. Both have the filter on the frame rail after the selection system as a shared item. Won't be hard to tell which system you have, the large selector valve unit has 6 lines on it and mounts to the inside of the frame rail near the drivers door, it was a retrofit to repair faults with the original design.

Strange These three didn't post.