Fresh air intake plenum leaks

Thanks for the prompt reply, 64dartwagon (wish I could find one of those). What's got me confused is the place where I see the water tracks. It's right at the junction of the firewall and the side panel, behind the fresh air ducts. Hard to imagine the problem is the wiper seals, but I do know that water can run from the actual leak to a point some distance away. This would just depend on the contour of the bottom of the plenum, I suppose. I have a set of the wiper shaft seals that schumaker sells (I got 'em from Dante's, but they look identical to some from engineswaps.com I saw a while back). Since I have the seats out anyway (as well as the radio and glove box) I suppose I may as well dig just a bit deeper and install those seals now. Thanks for the search suggestion, too. I read the posts that came up and learned a bit. Since the P.O. kept the car garaged, and I've only had it sitting out for a couple of years, I'm pretty sure I don't have any major structural rot. Removing the pugs in the firewall and blowing compressed air throughout with a long wand on the blowgun seems to have dislodged the builtup debris. At least I can't feel any when I stick my hands up into the plenum through the fresh air ducts.