I would look for a '10 speed' from Miyata, Fuji, or Nishiki, or other Japanese made brands... Centurion? Others? Preferably late 70s or Early 80s.
Also Raleighs from the same era should have mostly standard threading and sizes for replacements.
Lots of old bikes will have 27" wheels which are usually pretty straightforward to replace with 700 wheels, which adds a bit of tire clearance so you can run 35 or 38mm tires for mixed surfaces without a problem.