As I understand the guide rod mounts are also known as caster mounts or bushings. I'd reckon for setting and maintaining proper caster.
I haven't a clue on the diff mounts.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.