Does anyone know how one would go about fixing this area on both sides behind door

 

Better pic

 

From what I can see you would have to cut open the quarter panel then cut and repair the rust. If you can't see any damage from the outside maybe you could put some kind of rust converter on it and wait to repair the area. My .02

Larry

 

I can't tell from you pics if the rust has penetrated the panel. If it's just surface rust then I would try a spot blaster then muratic acid. This was covered well in a recent post (I think kyle's 77 started) titled phosphoric acid rust removal. If it has penetrated just cut it out, clean it up and fab some patch panels. I would treat the area after the repair with por 15 or something similar.

 

I sand blasted this area on my car with my weak blaster and smeared POR15 in there . I couldn't quite get my arm in there so I taped a brush to the end of a long piece of wood to reach in there . I sprayed some rust encapsulator in there also to get down where the two pieces of metal spot weld together . It was a real PITA and I never completely finished it yet . I bought some 1/8" OD tubing to fit down in the wheel well lip , and affixed it to the spray can nozzle . It was very messy . If there's rust in that spot on your car , more then likely it goes all the way around the wheel well lip . It just has not eaten through the metal yet . That's why I tried putting POR15 and rust encapsulator all the way around . I can't afford sheet metal replacement , so I tried this method instead . I also have a can of " rust fighter " but have not used it yet .

 

Oh , most importantly , I forgot . I ended up removing the back seat so I could get the entire rear side panel off ( the panel with the window crank on it ) There's a big access hole to where you can stick your arm through a lot easier then the hole in your pics ... so skip the brush on a stick advice , you wont need it from this access point .