Sumped tank or fuel cell?

If you are talking about an external electric fuel pump you need the inlet to the pump below the bottom of the tank -as much as possible.... I see many people with a pump in the trunk - and it will work, as long as you have a decent level of fuel in your cell. These pumps are not intended to suck fuel from the tank and need to have a good gravity head above the pump intake - at least several inches. That will probably bring on an arguement for the many that run trunk mounted pumps but I believe it is a fact.
Secondly, a 1/2 " fuel line is pretty big for a street car, IMO -and a 1/2" return is really, quite large. I would drop the return line down to a 3/8 at least. Lots of potential for cavitation after the pump.
Line size is all about line velocities (after the pump). In just about any flow situation the ideal flow rate should be a minimum of 5 ft/sec to a maximum of around 12 ft/sec. Too many glasses of wine in me tonight to figure this out in more detail but if you can calculate it out you can figure out the best line sizes for your pump size and fuel consumption (gas motors use fuel at a pretty close ratio of 1/2 the Hp they put out , in lbs/hour). A 500 hp motor uses about 250 lbs/hour of gas at max output. Divide the lb/hour by the density of gas of around 6.5 Lb/gal to get the fuel used in gal/hour - times 60 to get it to gal per minute.

I'm starting to remember too much fluid dynamics so time for another glass of wine....:)