6cyl to 8 cyl fuel pump question

[Chevy nutcase]

I finally decided to add 2 more cylinders to my 66 and the motor I chose came from a 77 corvette. I've replaced a lot more in-tank electrical pumps than I have mechanical pumps so I'm wondering why the pump on this motor has a return line to the tank when the one on my 6 cyl does not? The pump in question is brand new and I thought it would be one less thing to buy until I noticed that 3rd port. My first thought was having to buy a new sending unit that has a return and running a new line until I looked up a factory replacement pump for a 66 v8 and they don't seem to have a return line. Would I be ok just getting that style pump or am I completely off base here?