Rust in my 83 GMC rockers

[Jeepwm69]

My 83 GMC has been outside it's entire life. When I moved off for about 10 years, Dad tossed a rock through the back glass with a mower, and parked it around back with a tarp over the busted window. Over the years I'm guessing debris/leaves etc got in there and kept things moist, so I have some rot.

My question is, what all needs to be cut out here? I see replacement panels are cheap and all of them are available, but I haven't cut into a GM like this before.

Who makes the best panels? I know in the Jeep world they are NOT all created equal. Classic Enterprises is the go-to for Jeep panels. Is there a supplier for these squarebodies that makes a superior product?

First three pics are of the driver's side. The 3rd pic is where the floorpan meets the kick panel under the e brake.