I've never seen anything specific about correcting an out of balance propshaft in the W123 FSM - perhaps Zulfiqar knows where to find it?

There are pictures in the W123 showing the marks that should be aligned but as you mentioned earlier pre-about 1981 propshafts weren't marked. In fact there's a note in the W123 FSM more or less saying "if you find that the marks aren't aligned please align them as we should have done this in the factory"...

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!