[69goatboy]

You obviously would need a FP with a return line, one for a 69 GTO will work.

Then the line itself, should be 1/4", IIRC. The factory snaked the line (with the fuel line) through the driver's side frame near the upper control arm shaft area. If you choose to do this, remember some sort of protective cover for the line to keep the line from chafing on the frame. (I used battery cable loom on mine).

Then you'll need a sender unit with a return line port (I know my 69 has it), for that is where the return line will be plumbed to. Not to the pass side front port of the tank itself. That's a tank vent.

I think that should be it. Please, somebody correct me if I was wrong anywhere.