I would not attempt to feed a 500 plus HP engine with a 5/16 fuel line. IMO, a fuel system needs to be able to supply more fuel than the engine can use at full throttle high RPM. If you're near the edge with it, I.E. almost adequet but just a little to weak, you may not realize that your not supplying enough fuel. A fuel system that is too small will perform fine if the only thing you're doing is cruising and occationally stabbing the throttle for short bursts, say 1 to 3 seconds or so, but if you really ring it out as in going to the drag strip and racing, or longer duration top speed runs you can be running the fuel bowls on the carb low and the engine will go lean without it being totally obvious. FYI, Clay smith Engineering sells a nice high volume mechanical pump that can handle an engine like yours. It produces 16 PSI of pressure so you have to run a regulater and a return line. You could use the 5/16 line as the return but you have to plumb it so that it returns somewhere near the top of the tank. The Clay Smith pump is $155, you don't need to go through the hasstle of the elecric pump and wiring install and best of all, no electric pump whine noise.
