Dealing with Rust

[IDC10]

How do I best deal with the light rust inside the cowl of my '68.
I really do not want to drill the spotwelds and pull it all apart.



Do I need to cut this metal out at the bottom of the windshield and weld in a new piece? Or should I take some rust neutralizer (like Loctite or phosphoric acid) to it?



I want to epoxy prime the firewall, re seam seal with a 2K sealer, then paint it in a single stage GM light green to roughly match the rest of the truck. I'll also take some epoxy primer around the windshield frame, seam seal and paint it in the GM white.



Strategy is to rock the faded paint and run a patina truck for awhile. I've rebuilt the entire chassis...just need a cab to go with it. I'm too lazy to do the rest of the bodywork for now, but wish to preserve the truck from further rust.