Same truck, new (old) leak

Sooooo..... got the leak in the front fixed.... then my wife tells me the carpet is wet again after a rain.... original spot dry, cant reproduce any leak, start looking around, reading AF..... find air vent between cab and bed, on drivers side, POURING in under the finising panels, into the floor channels and straight to the front.... Is there a way to get a good seal without pulling the bed???
A GM guy, but come on already.......

Long shot, but check the third high stop light to see if the rubber around the light fixture is worn out. Mine leaked for two years before I figured it out. Leaving puddle on right side rear door because I usually parked with the right side lower.

Definitely look at 3rd brake light. Dodge rams, has a foam gasket that does nothing to seal. Got some rubberized weather stripping from Lowes.
2nd thought. I can't see it in the pictures of colorados. Is there a rubber molding on your roof couple inches away from where the top of door closes that runs from the rear forward? If so, my ram. Under that rubber molding is where the roof is joined with the sides and is welded and sealed. Took me forever to find that leak. Pulled the molding up, got some 30year clear silicon laid a bed down and pushed the molding back down in it. If you don't have the molding, then disregard.