Do I need to run a return fuel line to the tank?

I have a 440 with Dual Quads in the works. I have two 500cfm's and I am upgrading from the stock carter pump to the Street pump which is listed at 110gph. Where exactly do I put the return line? I have a Russell union -6AN x -6AN (my fuel line from Carbs to pre-filter is a -6AN, then from pre-filter to fuel pump is a 3/8"NPT hardline) On that union mentioned above there is a threaded port for what looks to be a fuel pressure gauge. I already have a pressure gauge further up the fuel line. If I have to install a return line, can I use the 1/8"NPT port?

i use a product engineering regulator and there return kit, high and low port is used for the return, heres mine.

I'd like to know this too? I have the same set up on my 512.
If so, why do you have to have a return line? Just curious

I assume to help with vapor lock and there is no way 110gallons per hour could be used on my motor, The extra fuel has to go somewhere. I prefer it to go back to the gas tank and not rupture a line