Fuel return line

I think all that sounds fine. Thomas Tornblum has a good EFI site at www.detomaso.nu/~thomast/efi
where you can see a picture of his banjo fitting and specs. I did my EFI very similar to his but used a different (speed density based) ECU. I used that top port for return line, but my very early pushbutton model probably has a slightly different tank from yours. I think I saw someone suggest using at least 10 AN for the supply line, though I can't remember what we used on mine. I did go through one fuel pump the first year, Corvette-sourced. So far so good on the second pump. Thomas suggests a couple on his page. I think the stock fuel cap is already a vented cap from what I have read. I'm no expert on emissions, but almost no U.S. cars run charcoal canister, and most U.S. cars probably never had them to begin with. Good luck. I'm sure some others will chime in here, too.

Yes, That is a problem. You cannot use the vent line for the return. First, you would have no way to vent pressure from the tank. Second, and EFI car needs the return line to be below fuel level. Why you ask? If you splosh fuel into the top it does two things. Makes it evaporate more, and puts little bubbles in the gas. Little bubbles get sucked into the pump and can do nasty things.

I suggest taking the filler neck out and soldering a piece of 3/8 steel line into it through a drilled hole and run the line to near the bottom of the tank. That can be the return line. Or use the fuel sender pickup for the pump inlet and the early fuel pickup tube as the return.

In my car,I feed the pump from the bottom of the tank with 1/2 inch hose and return in the stock fuel pickup. No problems.