I was hoping the truck was used for a pool service and the rust was contained to the rear.
If the rear is this rusted I imagine the front is as just as bad.
I live in Palm Beach County Florida in the Tri county area I have available to me countless Rangers available rust free from the mid 90s to the 2004 for anywhere from 500 bucks to 1300 bucks that need mechanical repairs.
here is just one example
I suggest you reconsider attempting repairing your truck.
Locate a truck from an area that does not use salt on their roads and restore that truck using parts from your truck are good.