Adding a return fuel line to factory tank

[mike's1965]

I bought a Edelbrock Pro Flo 4 multi port fuel injection for the 396 in my truck.

Also waiting for the sump fuel pump to be processed and shipped, it's currently a free rebate until end of October if you buy any pro flo 4, it allows you to keep your stock tank, and uses your mechanical fuel pump(or electric pump for carb) to supply fuel to the mini sump with a electric fuel pump inside sump submersed in fuel, then pumps that up to whatever pressure you set for pro flo, or other fuel injection setups.

The sump kit requires a return line to fuel tank, according to tech support at Edelbrock, it's because the pump can warm up the small amount of fuel, and if it gets pressurized from heat, it needs to be sent back to tank for safety reasons.

My truck still has the tank behind the seat, where would be a good location to add a return?

I was thinking possibly through the sheet metal of the sending unit.