1984 chevy leak

you have a water leak when and in what type of conditions does it happen?

When does it leak water Glenn? When it's raining or when it's dry out? What side of the vehicle? Check to make sure it's water and not coolant. Your heater core is on the passenger side. What Vent's? Lower or Upper? If it's the upper ones, I guess it could possibly be a windsheild leak.

Let us know.

I seem to recall a lot of chevys with badly rusted windshield frames. you wouldnt really notice the rust as it was underneath what looked like good paint , unless you tried to replace the windshield, but then it could turn into a nightmare as the rust would all crumble awaywhen you pulled the glass out. leaking was always a tipp to the problem. I Hope you only have a minor problem dude !