I don't know about other models but the early 380SL (81-83) are the ones with the weak chain unless they were upgraded to a double roller. I believe all 450s have double roller chains. Mine is a single in a 1981 and I changed it at approx. 85K and am ready to replace it again at 151K. Important as well is the tensioner. Before replacing mine the first time I could hear the chain rattling at start up because the tensioner was weak. I was lucky I did not have a major failure.

This may ease your mind a bit but my knowledge is limited so don't rely soley on my reply.