Well folks, I think I've found a source in the Atlanta area for this work. I'm going there today, and will give you a complete update.
I've thought about doing it myself, and may do that with the body panels. But the chassis is a different story. All the nooks and crannies of that beast present almost unlimited opportunity for huge amounts of messy, frustrating work. The difference is with the equipment. My 6 hp compressor and Northern Tool sandblaster just can't compare favorable with the commercial equipment.
Alkaline/acid dipping was my first choice due to the greater coverage of the inner parts of the box frame. But the closest place I found was in Indianapolis. The trade-off in time just didn't make sense in the long run. There are products and methods available for treating the inside of the frame without dipping, so I'll go with that. As long as the rusting process is arrested, things should be fine. After all, when we finish these cars, they are garaged, driven only in good weather (for the most part), and generally babied far beyond what they experienced in their first lives.
More later. And thanks, everyone for the very useful and greatly appreciated advice.