I know this has been discussed and lots of good information has been found, but I am looking for information specific to a higher horsepower (450 HP) application. I see my options as being; Option 1) Use the stock in tank electric fuel pump with a bypass regulator at the carb. This would incorporate the existing hardlines, 3/8" supply and 5/16" return (I think these are the stock line sizes) lines to the engine bay with braided lines to / from regulator. My concern here is, will these lines at the higher pressure be sufficient to provide the fuel supply required to the carb at WOT? Option 2) Replace in tank electric fuel pump with a pickup. Install external electric fuel pump with appropriate lines (I have a BG220HR fuel pump which BG recommends - AN10 lines to / from bypass reglator) Here is the recommended install. My concern here is location of the fuel pump in relation to the fuel line pickup in the tank. (Note: I do not want to add a sump to the stock tank) Assuming the best location for fuel pump is below the lowest point of fuel tank, I am concerned about the fuel pump having to suck fuel up from the tank bottom, out the top of the tank (stock fuel line location) and then down to the fuel pump. I think once it has been primed it may not be an issue, but it may be difficult to prime. Am I worrying about nothing? Will the stock hard line to fuel pump be of sufficient size to feed this demand or does it need to be upsized as well?

The 396 puts out an estimated 450 HP at sea level. Last night I ran my first-ever nitrous pass (100 shot); depending upon which internet HP calculator you believe, somewhere between 500 & 530 flywheel HP at altitude on spray. All this through a 3/8" aluminum fuel line, stock 3/8" pick-up (with pick-up sock, no pump inlet filter), fuel pump mounted about level with the top of the tank on the frame axle hump, E85 which requires more fuel volume than gasoline.

When I installed the electric pump earlier this year, it didn't have any trouble priming. Ditto after that pass where I ran out of fuel.

Summary: A 3/8" fuel line is fine for 450 HP. A Walbro 255 in-tank would supply it just fine as well.

That all sounds worthy of trying. I am surprised you mounted the fuel pump level with the top of the tank but I guess as long as there are no leaks it should maintain the pumps prime.

What type of fuel pump are you using?

As I already have the BG220HR fuel pump I am going to carry on that path. I'll replace the internal pump with the pickup sock and connect it to the pump using the existing 3/8 tube, using the 5/16 as my return. Then hang on!

I'm running an Aero SS, I believe it is.

I only mounted it up high to keep it out of the way of things. The aluminum line is very good about sealing.