You can't really get too much fuel pump unless you are talking about the $$$ expense, or possible noise. The return line takes car of extra flow/pressure. Here are some recommendations that I worked out according to formulas I found in Four Stroke Performance Tuning by A. Graham Bell. Running at 80% of plump capacity helps ensure a long life from the pump. Hp is considered at the flywheel.
_____________________80% of Max______80% of Max
Ford EFI Options_______N/A Limit________Boost Limit 110 lph________________240 hp__________200 hp 155 lph________________340 hp__________280 hp 190 lph________________420 hp__________340 hp 255 lph________________560 hp__________460 hp
Not a major factor, but worth considering… Also consider that a dramatically oversized pump will push large quantities of fuel through the fuel system and back via the return line. This process will add extra heat to the fuel which will lower its density. This is probably not an issue for otherwise healthy computer controlled efi motors, since the O2 sensor will help the computer to adjust the injector duration. This could however lead to increased wear on the injectors/pump/hoses of the fuel system.