Well, I thought I'd stopped the source of the leak by sealing the antenna grommet from the inside of the Jeep. But, a rather wet season following that proved otherwise. Yesterday I removed the front right fender and this is what I repaired (linked pic), by day's end, by cleaning and grinding the surface rust off. Surprisingly, there were no holes rusted through the cab wall. What I did find was crumbled and largely missing sealant from points where water could enter. After a final cleaning I brush-painted the areas with silver Rustoleum enamel and, when dry, applied clear 100% silicone sealant to every possible point where water might enter. I got the fender reinstalled this morning. Now, the wait and see begins.

Some time ago I'd already removed the cowl panel and ruled out that area for water entry. Still, I installed a cover I made from roof flashing over the cold air intake feeding the HVAC box before closing it up.

https://app.box.com/s/u64gidqr1fkiv0w5xnhfczzqdae508zx