The return line keeps the float bowls from overflowing due to overpressure in those rare instances when a 460 isn't guzzling fuel. The fuel pump has enough capacity to keep up with fuel demand at full throttle, but it's dumb, doesn't know what the demand is. The return line is a way to smarten up the system a little.
If you're replacing the fuel filter, a transparent one isn't a bad idea. Lets you see when rust is becoming a problem.
1988 CVLX Formal Roof (Love Boat) POTM July 2019 & Aug 2020, 55K
E-code lights w/ relays, LEDs w/ switchbacks, 15x8 Ansen slots w/ 255/60 BFG's, Kenwood stereo, various hacks.
1988 CVLX (Destroyer) 1998-2001 driven to death 202K
1988 Squire (Chris Craft) 1996-1998 junkyard rescue driven to death 199K