From some of the threads I've read regarding the OVP, the electrical techs have determined poor soldering as the cause. Some have even gone as far as resoldering the joints on their old OVPs, thus "restoring" them back to usable condition.
Don't know how far back the OVP goes with regard to model years, so I can't say whether the 76 SL would be plagued by that. Maybe an MB tech here can answer that.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car