how do you install return lines?

Even though A-body tanks are fairly cheap, I wouldn't mod the tank, plus that can be dangerous if a used tank. In my C-body, I drilled a hole in my factory sender and installed a brass fitting w/ O-ring seal. In my A-body, I bought a new 3/8" sender w/ 1/4" vent tube. I return thru the vent tube but measured 9 psi back-pressure using a Walbro EFI pump. I need to try flaring the vent tube for less restriction. If I had a good welder, I would buy a non-vent sender and weld in a stainless return tube. A few people have added a return stub to the fill tube, but I wouldn't want to molest that factory part.