I fed each end of the SP rail with a -6 AN
line, one from each in-tank pump. IMO, nothing larger than -6 AN is called for unless you're going to be making more than 1000 RWHP (the smaller-than--6 factory line supplies enough fuel for more than 500 RWHP, so why would you need more than 2 -6 lines to supply fuel for, say, 800 RWHP?). IMO, larger than -6 may even be a disadvantage because upon hard acceleration you have all that extra fuel weight in the line that must be accelerated. It's pressing backwards toward the pumps and could serve to reduce fuel pressure at the injectors. Not a good thing.
I installed a center-rail return on the SP rail. From the center return a -6 line goes to the Aeromotive regulator, then from the regulator to a fuel cooler mounted behind the driver's side turn signal, and from the cooler back to the tank.
Even though a lot of successful installers have done it, I don't like the idea of using Ts at the rail ends. If you do it that way, once the fuel goes into the rail it stays there until it's injected into the engine. I have no proof that it's a disadvantage on the typical Supra to inject high temperature fuel, but I know that certain fuel injected race cars have been proven to make more power with fuel from a cool can (containing ice) versus "engine ambient" temperature fuel. With my setup, fuel is constantly flowing through the rail and out through the cooler, so it should be a bit lower in temperature.
Steve