Fuel Tanks And Lines

You'll just need a tee for supply, and a high flow splitter for return.

I would avoid the balance line myself, though it is likely legal for that truck.

 

Plumb the return line from the head to the top port of the splitter, then out each side of the splitter to the return port of the tanks.

The splitter puts equal return to both tanks when set up correctly.

The supply will draw equally with a tee, as long as all lines are in good shape, same size, clean vents

 

I don't remember the exact size, but I replaced the splitter from your pic with this kind on my truck

 

The old mechanicals run better drawing from bottom. The fuel pressure caused by gravity helps them old pumps. The bungs on bottom of tanks were always just 1/2 npt. Tee at left tank to cross over to rh tank with a #10 hose from tanks to filter or pump. That is all you need. Return fuel to lh tank by plumbing to top somewhere. Usually a #8 hose or sometimes depending on pump set up it may have two return hoses. One #8 and #6 to lh tank.

crossovers are not illegal. The top draw system is Just new technology that was necessary for the new computer powered pumps to work. Many old trucks had top draw 50 plus years ago but that didn't work very well at all with mechanicals.

also with bottom draw you never have problems with water build up in fuel that sinks to the bottom and stirs up with every fill up.

 

Many older tanks used that siphon tube for returns so that the hot fuel would cool as it went back in to mix to alleviate vapor. If you’ve ever been around an old Cummins 220 or 250 they return the fuel back to the tank so hot even at idle that the tank breather looks like it is smoking.