I too have been down this road. I had a leak on the passenger side of my '80, for two (California) winters I was vexed with the wet floor problem. I finally figured out it was seeping in on the roof where the rain gutters are welded and running down the windshield pillar. It sure looked like the windshield gasket was leaking. In fact, the original seam sealant had given up the fight, so I applied urethane sealant from Home Depot and have been dry ever since!
