Just bought a 1998 GMC truck. When it rains, water will drip onto the floorboard from the blower motor cover on the passenger side. I haven't traced the water trail very well yet, but I am fairly sure it is coming from beneath the dash and up from the hood area where the hood meets the front windsheild. I don't think it is the rubber seal around the front windsheild. Instead I am suspicious of the vent area between the hood and windsheild. Any thoughts on this? How do I remove the blower motor cover to have a closer look the next time it rains? Carpet on floor board is getting wet. I sure would like to find the source of this.

Thanks in advance for any advice you might provide me,
dbteeitup

It may from rain entering the vehicle some place where it shouldn't. That can be easily replicated with careful use of a garden hose and someone inside watching for the water to show up.
But, also check the A/C drain where it goes out through the firewall. If that drain is restricted, condensation from the A/C system will back up and find a way to dribble out the HCAV case.