I read through this post again and wondered why I didn't think the W126 was my choice.
If I had wanted the Benz of the 80s, the W123 has a proven track record of reliability and easy maintanence. It may not be as refined as the W124, and of course, it doesn't carry the complex problems the refinement brought along with it.
Put it simply, you could identify what was wrong and get it fixed with much ease. And the beauty is that it hardly ever needs much fixing when properly maintained.
Detail it well, and it will look as stately as any other marques.
126 tailed by a 203, 129 leading the pack.