Looking at PIC reminded me why at least once a week I always tried to clean the bottom of my vehicles because of the salt crapola, etc, not just from the road, but the Atlantic also. ., Well before I got older and learned about Krown, Fluid Film and other items. FTR, I am a Shore Kid,
OP: As a minimum I would replace all those brake parts and the back shields also. Another thought complete rear axle replacement, But all depends upon what U wanna put back into an apparently rusted older vehicle. IF I ever moved back home (as in NJ), I would be Fluid Film coating or Krown coating under my vehicle. I have a TEXAS truck and it definitely is not set up to run in those conditions ref road salt etc.
CAVEAT: If the back that bad, how does the front look to include suspension, brakes, rotors, etc,., hmmm.