[pilotj]

I had a similar problem on my 79 pu(water in passenger side floorboard). I thought is was my winshield leaking, so I replaced the gasket. Still leaked. Finally found out it was leaking where the firewall is joined with the cab. I happened to be be cleaning the cowl vent area with a water hose and noticed the water had leaked in from the cowl vent(fresh air intake). I pumped a tube of clear caulk into the body/cowl seam and it hasnt leaked since.