Its a pity vw had not put a squirt of wax preservative around this area ! Once the repairs are done and painted, thin down some waxoyl and allow some to penetrate from the top.
1992 red lle 2.2 subaru 1990 rhd caravelle 2.2 subaru 1986 california import vanagon
Plan is to zinc primer panel and rail before spot welding back on. Will cover in rustoleum paint and run a bead of tigerseal on the top of the rail. May even tigerseal the rail cover to stop the rain seeping in as I can't imagine taking it off much after repairs.
1987 VW T25: Subaru EJ20 using RJES parts (If it was meant to go fast it wouldn't be brick shaped!)
You could use panel bond instead of tiger seal. Some types are weld thru so with the zinc primer as well it will really keep moisture out with colour on top