[dubds10]

Windshield and firewall rust is the worst and I stay away from any truck that has it. Looking at those pics, it looks like you have issues that were just covered up by paint and weren't fixed previously. Personally depending on the cost of the truck and what you're working with, I would just clean the truck up as best as possible and maybe lightly sand down the suspect areas and repaint them to look decent and protect the metal. At least give a good 10 foot appearance until a time comes that you can replace the cab or actually get all the rust fixed properly which wont be cheap and of course means tearing the truck apart.

The main issue is once a truck is torn apart, it rarely goes back together in the time frame you expect. Or you find another truck that's rust free, since we have a ton of these trucks here in the PNW and then sell this one unless there's sentimental value to it.