[Gunner]

Typically only FI systems and high-volume electric fuel pumps need return lines. Webers are just carbs, so unless you're running something unusual, 3/8 fuel line and -6AN hose and fittings all the way should be fine.

Webers don't typically take any more fuel than a dual 4BBL (or a single, for that matter)... it's just divided up among more individual metering units.