[GTOYANKEE1970]

Jeff
In my humble prof opinion, Although POR products do a fine job for what they are designed for, they are nothing but bandaids. All any of those products do is slow the rusting process down. The only way to truly remove rust is usually more involved than the average person wants or can afford to do.
From the pics you have your in a tough spot to do much with the rust in between the panels. Without seperating the panels and either sandblasting or treating with an acid wash all you can do is slow the process a bit. Ask any reputable resto shop and they will tell you the same thing.
I went the route of acid dipping a floor pan I salvaged from a doner car for my 70 GTO before welding in at all factory seams.
Let me know if you want to talk some more and I'll give you honest advice, not that the POR type products are bad, it's just what you want to accomplish.
John