POR-15...

Let me tell you about the beauty of this stuff.  I know it's not "factory", but neither is the rust that comes with a 45 year old car.

POR-15 works like it says.  It stops rust.  I ordered the floor pan and engine kit from them directly.  Starting in the trunk, I removed the fuel tank, and all of the sound deadener that was left.  After countless hours with wire wheels, and wire brushes, I started on the POR-15 process.  Clean it with Marine Clean, spray it Prep&Ready, then hose it off, and let it dry.  I used the gloss black pint can on the trunk, coating every surface.  Then the Power Mesh for a small hole that had eaten through trunk floor, then another coat on top.  Filled in the pits with the epxoy putty, another coat of POR-15, and the trunk looks brand new.  It's hard as steel, won't chip (I tried), and is ready for primer and paint. 

After the trunk I moved to the back seat, and repeated the process.  Overall the results are amazing, and I can't believe people don't use this more often...