I don't see any holes big enough to sling a dead cat through. That's always good.
What is your long term goal for the truck? Daily driver? Show stopping gem? Somewhere in between?
It will not be fun wire wheeling all of the rust from the floor and nearby rusty areas. Sandblasting is no joy either.
If it's going to be a daily driver, I recommend that you remove all of the paint and filth and any chunks of rust, vacuum or blow it clean, then treat it with Ospho. This product will convert the ferrous oxide (rust) to ferrous phosphate which is inert and stops the rust process. The process may leave a white powdery dust in the pitted areas which you will need to remove. The white powdery dust is a byproduct of the process. The best way to remove it a day later is to use a scotchbtite pad wet with Ospho. It will clean it right up. I then wipe it down with acetone and prime and paint.
