New Project '65 Cuda - Gonna need lots of advise

I believe you need to scrape out all of the old caulk to get a good look at the rails for rust. I used the "can opener" method to get my rail trim off, I did buff smooth the opener's paw to keep from scratching the chrome. The Wood method works as well. The most important thing is to "go slow," do a little section at a time. If you bend one,(trim) it's hard to repair. I haven't got to the "re-caulking" of my rails, but you need to use a quality product. I believe this has been discussed on the forum, of what product to use.
Gas tank? Yes, I installed a new one along with a new fuel level, (and engine fuel pump) sending unit and new hangar straps. It's an easy job to do, (and not real expensive) but before you hook up the fuel line, disconnect it at the fuel pump and force (blow) a good solvent through the line. you will be surprised what comes out.
Keep asking the questions and everyone here will give you the answers and advice you need. Keep us informed of your progress.
Norm