Chrysler NEVER did and you MUST not vent into the trunk. Further, having, not having the early vent will have nothing to do with how the tank fills
PLEASE PLEASE do yourself a huge favor. Go over to MyMopar
http://www.mymopar.com/index.php?pid=31
and download SEVERAL factory shop manuals. 69 for certain, because it shows the early vent. 70--through 73, and read the fuel sections about "tanks" and the emissions sections about the evap / fuel system.
I posted this earlier and evidently you didn't see it or didn't read it. This is a good rendition of the non CA / early 70 and earlier vent. It comes out near the top of the filler, hooks to a tube, and bends UP near the top of the rear quarter, then down alongside the filler and OUT THROUGH the floor gasket and the tube ends "open" in the rear frame rail. IT IS NOT open to the trunk