An update on this little story... I made the repairs, sanding down to bare metal (mostly), applying rust converter, priming, and painting (surprisingly enough, the $4.95 can of Dupli-Color Truck, Van, and SUV (perish the thought) spray paint matched remarkably well, not that the problem was in a visible area). Ditto the underside, except I hit that with some undercoating.
What's interesting is that while I had the battery out, I decided to top off the cells with distilled water, bringing the levels to the bottoms of the slots, which may have been a tad more than specified but I figured no harm done. I reinstall the battery, insert the vent tube through the grommet, and drive off to do some errands around town. Twenty minutes or so after getting back I notice a wet spot at the right rear, I look underneath, and sure enough the vent tube is practically peeing, leaving a cirlce of battery acid in the driveway about 12" in diameter, which I guess represents roughly the amount of water I had put in the battery. All this was a few days ago and I haven't noticed any subsequent "urination," but this was the first time I've ever noticed anything like this. Anyone know what's going on?