I am thinking about having the return go to the aux tank, and then have a small overflow line to the main tank.
The selector valve will only be for selecting which tank the pump draws on.
As for filling, I am leaning towards a second fill neck (with sealed cap) that comes through the side of the doorstep just inside the driver door.
Diesels trucks have both tanks plumbed together, so the level in each is always equal. This would let you simplify the return plumbing and supply hoses. If the connecting line was big enough, you could fill both tanks from stock location, assuming they are mounted at equal hight. This would also let you use only one sending unit for the fuel gauge.
I like the idea of plumbing the tanks together, but am worried about the connector line being low to the ground and susceptible to damage.
Maybe there's a work around?
How big is the connector line on the diesel trucks you're thinking of?
Is it ok to route it from the bottom of the tanks, but then up and over the frame? kind of like this: O_
︹_O
