Cowboycoupe

Following up on the help, I got under the truck, and found a small rubber drain shaped like a letter "L". It's on the right hand side of the truck, just a bit below and to the right of the two heater hoses going through the firewall.

When I messed with the fitting, and took it off, a small amount of water ran out of the metal fitting coming through the firewall. I did as much as I could to rod it out, using things like zip ties, wire, long wood screws, and so on. As I did this, more water came out, but not really a lot. Have no idea if there's another fitting, or whether there's some crud in there blocking the drainage.

At least the rubber drain fitting lines up almost exactly with the location of the leak.

I have no idea whether that was my problem or not, but I'll keep an eye on things to see if my problem continues. To be continued after the next rainstorm...

Cowboycoupe

Hope I'm not writing this too soon, but we've had a couple of really intense rain storms over the past three days, and the leak appears to have been fixed. Truck stays nice and dry. Thanks to those who suggested the AC drain. Although nothing seems to have been blocking that drain (no lumps of crud came out), it did run water out when I removed the rubber elbow, and when I poked around inside with different tools.

On to other stuff for the truck now.