Any 4.6 after 98 is on a returnless system. 42's are fine. Don't go w/ an FMU. Upgrade the pump in the tank.. Either a aviator pump or if you want over kill look up the bosch 044 pump. $200 and its rated close to 300 lph. Plenty of fuel. No need to upgrade the rails. Those hypereutectics will fail much before the rails need to be upgraded.

-Mark