Mechanical Vs Electric Fuel Pump

If you are keeping the stock tank run an external pump.

The GPH requirement formula is available online if you want to be scientific about it. Just google it. But most manufacturers will tell you what size you need. I.e. supports up to 550hp..etc. How much HP are you making?

A return line is sometimes mandated by the manufacturer of the pump. It is always a good idea. but not always needed.