Interesting topic. I had a w123 240D manual trans. in the early 90's and wanted to get another one. I was however, concerned about being able to keep up with modern traffic.

It was completely fine back then when the speed limit was 55 and people would seldom go over 65 on the highway because police actually patrolled traffic. Today when I see someone pulled over on the interstate I think "geez, I wonder how fast that guy was going to actually get pulled over" seeing as the speed limit is now 70 and seldom is the traffic travelling at less than 10 over. I just remember the 240D being pretty "busy" at 65 and up.

Turned out to be a moot point as a nice '85 300SD popped up on my local craigslist, it was local, reasonably priced and too nice to pass up.