Rusty rear frame rails

In my quest to get a solid frame under this car before I start chopping the roof off I found some more rust.   I don't think it would have taken a rocket scientist to figure out that there was going to be more rust, but I found it on a spot of the rear frame rails that didn't look rusty.
I was under the car cleaning the rear frame rails off with a wire wheel on my pneumatic tool when I uncovered a tiny pin hole.  I tried the screwdriver method of inspection.....that's when you hit the area in question with an old screwdriver and see if it makes a hole.  If it does, you have bad rust and now a hole in your metal, if it doesn't it's called a patina.
I guess I'm ordering a full rear frame rail now as well.....or maybe just some of the pieces that are really bad.

Passenger side frame rail with a couple holes of rust before the screwdriver test.

Passenger side Swiss cheese after wire wheel and screwdriver test.

Drivers side frame rail after the wire wheel, but before the screwdriver test.

Driver's side frame rail that actually surprised me when it failed the screwdriver test.