The fuel tank vent line you refer to may be plugged, if that suits you. Another option is connecting it directly to the vacuum carburetor inlet.
If your goal is put stuff back to original look and function, seek a replacement cannister, and connect it back to the vent line and connect the cannister back to the vacuum port(s) at the carburetor throttle plate inlet. As shown by your image in post #3.
The cannister's purpose is to accumulate fuel vapor while the car is not running. A prime example is while sitting in a parking lot, and as the day heats up, the temperature within the fuel tank rises slightly generating fuel vapors that would otherwise be vented to atmosphere. The canister accumulates these vapors until the car is again started, when the vacuum port at the carburetor sucks them into the engine to be burned.
The cannister has a limited capacity, so were the car sitting in the hot sun all day, or parked for several days, at some point, the vapor backs up through the carburetor and escapes to atmosphere and may be detected by the odor. The purpose of the charcoal is simply to minimize odor, with little benefit to the environment.
Without the holding capacity of the cannister, connecting the vent line directly to the carburetor may still result in fuel odor, but at least while the engine is running, you (and the environment) will enjoy the added benefit of those vapors getting burned.
As for the return line, this was present from the factory only on 426 Hemi and 440 HP cars. The line routes from an extra fitting on the fuel pickup, and exits low on the passenger side of the engine down at the frame rail. It then connects to a tiny cannister (vapor separator) on the output side of the fuel pump. The return line is only necessary for issues with vapor lock, and it's not the only way to resolve the issue. But this was the factory option to do so on those high performing cars that may run hot under street racing conditions.
