Hi Doug.....good to have another Lower Mainland guy here !
You don't say what type of truck you have, but there aren't a lot of areas that allow water / moisture into the cab area. If you have leaks ( aside from actual rust penetration ), it has to be thru window or door gaskets, maybe a cowl vent or ?? Doors have small drain holes in the bottom to let out any water that gets by the gaskets on the glass. They may be rusted / plugged ?
You can purchase new rubber seals ( Steeles Rubber ) for most areas that may cure your issues. As for wet sound deadening material, you may need to start fresh once the cab is sealed up.

Last edited by britcon; 01/02/2013 11:28 AM.

1940 Chevy KC 1/2-Ton
In the Stovebolt Gallery