Unknown vacuum line

As noted, A/C cars only had vacuum for HVAC control, heaters only used twin cable mechanism. On 1970 California emissions followed by 1971 federal emissions there is a capped end vapor separator tube in the trunk ahead of the fuel fill pipe that is 5/16 hard line back to the three port right side valve cover breather. It connects to one of the ports, another port goes to air filter housing through 5/8 hose, and the other port goes to carburetor bowl vent. PCV is on left valve cover. To my knowledge, the vapor lines where always routed outside the car. I have seen otherwise, I just can't remember exactly on what, although I am wanting to say on a '71 charger I parted out. HVAC vacuum line source seems like it was 3/16 on the A/C \6 '71 Duster I had, and rubber line went through from manifold vacuum on left side and the hose ran through a grommet on firewall to the spherical reserve canister on top of heater box. Dart design is "different enough" from duster design, though. Just a wild guess, what size is the line that goes to firewall and does it enter and maybe exit back out somewhere behind the right rocker panel under the car on its way back to fuel tank?