I'd include Model A Fords, most Packards and many Lincolns. Some cars don't look right in a two-door closed configuration.

I had a friend who owned a Facel Vega (a "clamshell" four door design) in the '80s for many of the reasons you like your car.

To me the prime attraction of Mercedes models such as the SD is that they're amazingly robust, fairly cheap to buy and operate, and are likely the last cars to be built that you will be able to say that about. Be that as it may, owning and pampering a "delicate flower" Mercedes can be justified by this being a free country. Many of us had involvements with sports cars which we loved but which had running gear with the durability of chocolate. I have three Benzes also, but they're all low maintenance W123's, although the coupe was nice enough to be featured in a magazine.