I think you might have nailed the problem. I have tried everything I can think of to stop this leak to no avail. Don't suppose you took any pics when you did this? I'm not sure I totally understand how/where you found the leak.
Is it not possible to do from under the dash perhaps?

I tried cleaning up the seam above the fuse box and fiberglassed the works, but I still have a leak. I even resorted to pouring a bunch of fiberglass resin down from the cowl outside the truck. Still have a leak. Does this seem like the same spot to you, RichO?

Thanks for all the responses, Guys. Sometimes I feel I'm all alone in Toyotaland here in Central Illinois with no support. This forum sure is great.

T.