On the rheostat issue: The dash lights went out in my 450 SLC and I found that it was just a corroded fuse. A bit of sandpaper and the lights went on again!
I love the title of this review. That's only 5000 LESS miles than we got out of our 1975 Ford with less than $500 in repairs!!
I had a 450SL 2 Top (over 20 years ago), not an SLC, and these cars are quite heavy and slow. They are still a very nice looking car. Keep it garaged and polished, and they look great. They are nice safe cruisers at well over the national speed limit. They gradually climb and hold higher speeds well. I would not buy this car to drag race, and the Supra would win in the quarter mile.
I had a lot of expensive emissions issues with mine and sold it. Parts are high on a Mercedes. Sit down when you hear replacement parts. Why do you need 2 posts on the top of the shocks?
The key locks broke in both my trunk and my ignition. The ignition tumbler was a nightmare to replace.
Make sure you have 2 oil pans under the car when you change the oil.
If you want to add rear speakers to your new sound system, don't drill into the gas tank. I bought a new sound system from Crutchfield and it was simple.
The removable top on a SL is very hard to put back on, even with help, so I rarely used it. Some get a ceiling hoist. Hard to unlatch and then line up the latch. I used the soft top. Very confining I found with the top on, but I did use mine in the winter.
I changed my 450SL in 1989 to look like the 560SL; front new wheels and color matching trunk deck light.
By the way, my son's Viper was number 2 on a dyno board below a Supra. No doubt mods were done. I know my 450SL wouldn't beat a stock Supra. I never carried furniture on my very narrow hard top either. I still drive convertibles today; now a C5 Vette.