Let me preface my response with this: After growing up in NE Ohio and dealing with salt exposed vehicles for 20+ years - I'll never own another rustbelt car again.
So, I'd say it depends on what you're planning.
If it doesn't concern you much, or this is an interim vehicle for just a couple years, you could spend a few days wire-brushing all the rust areas in these pics and shoot some Rustoleum and probably have pretty good results. What you aren't seeing in these pics is the rear spring/shock buckets, the brake internals, the engine compartment, electrical, etc. This is where the salt really does damage that maybe isn't initially evident, but can and will present issues in the future.
If you are looking for a long-term truck then I would be inclined to continue the search for a rust-free vehicle. 3rd gens are so common there are bound to be better specimens. Perhaps consider a fly/drive scenario... in my opinion even a few hundred bucks for a plane ticket would be well worth it in the long run vs. battling rust. I know here in PHX there are a plethora of comparable mileage 3rd gens for sale in a similar price bracket. I'm sure you could find a rust-free truck in a market closer to you as well.
That said, I don't see anything in those pics that screams "impending major disaster".