Is this car carburetored or EFI? If it has EFI, then it should have a return line although there are some "returnless" systems.
Anyway, yes you could reinstall a vapor separator system although I don't know how available the parts will be, you might need to develop something of your own making. Part of your problem is the unplugged nipples are right there at the tank, in the factory system they ran lines up to the engine compartment (to the canister).
I have vent lines on both my Challenger and Cuda, both are on the fuel filler tubes. On the Cuda, my line runs from the filler tube (near the tail panel) to the right side of the trunk to a bulk head connector that vents under the car. On the Challenger, much the same deal except specific to the Challenger. I do not have a gas smell, but I do have a large shop which might mask it.