OK, I assume you bought the car torn down? With no fuel tubing? You probably should invest in a factory shop manual, either on CD or reprint. Newest one we have here on this site for free download is a 72. I would guess the fuel line routing is SIMILAR
http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download
You should be able to figure a way to tap into the existing ports on the tank and use one for a return port. You MUST figure out how to vent the tank. Newer cars with that system used a "pressure vacuum" cap, which means that there can be a certain amount of either pressure or vacuum in the tank, before the cap "pops off" sort of like a relief valve.
Older cars had an OPEN vent that was welded into the fuel filler tube way up high before it exits the side of the car. The tube went down the backside of the filler tube, poked through the rubber gasket in the trunk floor, and hung down into a hole in the rear frame rail. Older gas caps are sealed not vented.
So far as a vapor return, I'm a HUGE believe in 'em to help prevent vapor lock. You can use Wix 33040 (5/16) or 33041 (3/8) fuel filter, both of which have an orificed 1/4" return line built in. You can mount these either vertically or horizontally, so long as you have the 1/4" fitting on TOP.
Below is how the older vent system worked:
Here's a diagram of how the 72 vent / carbon can stuff hooked up. If you are lucky, you still have the big liquid / vapor separator in the rear