Basically a Carb'ed RRC would be imperial and the thread is much tinnner but it's also a finer thread so as said is gets damaged, especially once it's rusted too.
Later (EFI onwards) should be M20 the same as the front radius arms which changed at the same time (thicker axle bushes etc).
The axle to trailing lnk bush remained the same AFAIK, along with the A frame and Panhard rod.