Electric fuel pump (6pk) is return line required? If yes how would it be connected/ routed. Maybe pics. Thanks

I would T near the carbs & run a line from the T to a holley blue reg & use it to regulate the return volume to control the psi at the carb inlet(s) to where I want it (at least several PSI at the carbs at WOT) with (I am assuming) adequate ID lines from tank to carbs for enough vol for your requirements.

what brand and pressure and volume pump are you using?
Some big pumps need the fuel to circulate to keep them cool, others sizes don't
Contact the pump maker and ask them about this

This is a very generic question. What is your application? Street, Street Strip, Strip Street or Strip only. Keep in mind the original mechanical pump had a return system .060 return orifice for vapor lock. In most cases a dead head system works just fine. A friends 340 6 pack stock eliminator car found no improvement going to a return system and he went 10.60's many years ago.
I am learning that high volume low pressure (below 6psi) works best. I am working on making 3/8 aluminum fuel line to replace 5/16 steel line to each carb on my race engine. My race pump has a bypass built into the pump it is set at 20psi and returns to fuel cell and delivers that pressure to a deadhead regulator set at 5.5psi.

Thanks guys

The line size from the regulator to the carb. need to be little, not a bunch, bigger inside diameter than the needle and seat size If you are feeding one needle and seat that is smaller than 1/4 inch, .250, then a 5/16 I.D.,.312 is more than big enough
I see guys at the track with #8 AN lines feeding the fuel bowls on Holley type carbs, feeding one needle and seat, not needed IMO
A #6 or 5/16 I.D. line should feed two .120 needles and seats at WOT with no issues, the bigger the I.D. of the line the more pressure put onto the needle and seat hence needing to reduce the pressure to keep them sealing

Sorry but you will gain nothing and make your fuel system worse by doing so. Complete waste of time and money. 1 carb does not need 3/8", 3 carbs sure does not. Only thing it will do is slow up the flow of gas and give it more time to heat up.

What car?

I use a return line when using an electric pump. I use in tank pumps. I route mine same way factory does with return going into tank. Return line is not required. Lots of people don't use a return (deadhead). Lots of variables

I use a return line on my 455hp 289 64 Fairlane, -8.

1/2" it's a QuickFuel pump and return regulator.

It drinks fuel like fat man eats hotdogs at a contest, then it does 16 mpg on the highway. Kick the little Ford all you can, 11.50s in drive!

I bought a 3/8 line and installed it. I used the 5/16 as a return line. I installed a hemi fuel filter which is designed to have the return line off the filter, it can be identified by having three nipples. It has worked flawlessly for 10 years. I had to reconnect the return line to a different spot on the tank which in my case was on the new 3/8 inch fuel pick up and fuel gage sending unit. Good luck.