I am about to remove the bed to address the rear frame rust. Is there anything that I can do to fix this wheel well rust and prevent it from advancing?

 

I'm also working on my frame right now but I've got a flareside which has fiberglass sides. All I can tell you is to remove the sides of the bed and take a good look, you may be able to cut it out and patch it and that would be the cheapest way to go but they may already be to far gone. Take a good look at the bed also, I thought mine was fixable until I removed it and got a really good look.

 

I am brand new to this. so, my thoughts mean nothing.
But, you might look at what this guy is going at 6:27 where
he sprays something like Fluid Film into the *inside*, in this case via
the head-light assembly holes.
I am still trying to get answers as you can see here, before I buy a Ford:
As a novice's suggestion, you might 0000-steel-wool the outside surface and then
spray clear (uncolored) clearcoat onto the bare metal that remains.
https://www.ranger-forums.com/genera...famous-166086/