Sound deadening, Carpet, and floor pan repair questions

The previous owner of my lovely 64 dart allowed the front floor pans to get into bad shape. There were pretty bad water leaks i discovered after buying it, which have now been 99% solved (intermittent one or two drips periodically). I'm planning on buying correct gauge steel, cutting out beyond the bad sections, and patching it. It's no huge spots, by and large its all in good shape, just an inch here and there that he "solved" by riveting sheet metal over.

So I'll remove all of that, weld in new steel, and clean everything up. That's a great opportunity for me, the carpet is in bad shape and could serve to be replaced, but while I'm at it I would like to add sound deadening. There's a whole lot of road noise, especially when I'm on the interstate. But also, I live in the deep south- it's hot down here as is, and a steel box with no a/c jsut absorbs it all.

So my questions are, what's the best sound deadening for this? Dynamat xtreme seems good for weight versus effectiveness, and it claims to also reduce interior temperatures. I would also like to add a layer under the headliner, in the doors, behind the kickpanels (will be adding speakers there), under the dash, and on the firewall. Whatever is going to be best for this is what I want to do. Remove as much exterior sound as possible without being so thick as to make it inconvenient, and if it can keep heat from outside out and make whatever A/C I install later not have to work as hard, that's helpful.

Where's a reliable source for carpet? I know classic industries sells carpet but I've had issues with them in the past for other parts so I'm hesitant to keep shopping with them if there are other reliable suppliers. What's the best method for applying sound deadening in doors and upside down? contact adhesive?