Hey Norm,
My A/C evaporator was the source of my damp passenger floor board. There is a small 2 inch rubber hose that extends through the firewall to drain water (condensation) from the evaporator. In my case the hose had come off, so the water was draining down the firewall (inside) and accumulating on the passenger floor board. Its a long shot but if all else fails..........
Its very easy to find the hose, look under your dash (passenger side), locate Evap. Box (just below glove box), about 1/4 the way up the backside of the Evap. Box you will see the hose extending from it thought a grommet in the firewall. If it looks good, run the A/C for a bit. Turn the car off and wait a few minutes >>>> look for water under the car (behind passenger front tire). Outside temp plays a roll in this as well, so don't worry if you don't see any water on the ground. Repeat process on a warm day....
Most likely its the drains in your rockers, or a bad Windshield seal (aftermarket?) It helps to have someone run a steady stream of water around the windshield, while you wait inside and observe....