Just to chime in on the topic that I know more about than anyone else, here's the scoop.
5 1/2" wheels came on US-only 240D cars that didn't have optional Bundt wheels from about 1980 to 1982.
6" wheels came on US-only 300D and 280E sedans that didn't have optional Bundt wheels in about 1981 +/-. I believe the correct weight to be 11 pounds, compared to 23 pounds for a steel wheel the same size.
These wheels where never used in any other market in the world, and only on the sedans listed above for the years listed above. (people will argue with me about exact dates and I don't really care...)
I've used these wheels on my W114 coupe and on my W123 wagon and just loved them. The place I have noticed the most difference is on bumpy and curvy roads. The tires get back to the pavement a lot faster.
I hunted these wheels for about 10 years and have a good supply of them. The sources for them have dwindled substantially over the years, as the supply of scrapped W123s from this narrow time window has pretty much passed. I drove 5000 miles in my year of the most junkyarding and acquired several sets then. But that was a long time ago, and now they are rare, and now people snatch them if they find them because they know what they are. But the 6" rims are really very rare.
I have bought and flipped at least 4 cars to get the wheels off them, replacing them with Bundts and unloading the car. I have also swapped Bundts with people who are selling their cars and are willing to accept the wheel "upgrade" of a Bundt wheel with nice paint.
I have them tested for trueness (which no one else does) and they are stacked in my storage. Occasionally someone comes to me from somewhere on the planet and pays lots of money for them.
The really odd thing about this is most people wouldn't bat an eye paying $300 - $400 for a really cool modern 20" rim for their car, yet for some odd reason, some people think that that's too much for an older wheel, particularly from a more pedestrian car.
Shipping has grown increasingly expensive over the years, particularly to Australia.
Some people like to have them powdercoated. I figure it's covered by a full wheel cover so it doesn't really matter, plus it's going to get covered with brake dust anyway.
As for the wheel cover, there are special wheel cover clips that have a nylon pad (instead of bare steel) but otherwise look the same. They are available new from MB, about $5 each. They will ONLY fit the stainless steel wheel covers, and not the chrome wheel covers. I don't know why but I believe this to be true. So some people with a 1968 car for example probably have the chrome wheel covers and will need to get the stainless wheel covers to use with these wheels.
The aluminum wheels use the same lug bolts as the steel wheels. Absolutely nowhere can I find the torque specification for the lug bolt that is specific to usage with the aluminum wheel.
By far the most buyers of these wheels are W113 owners, but they also seem to go to 190SL owners from time to time as an attempt to get rid of their horrid 13" wheels.
There is a write-up on these wheels that I occasionally correct in the technical manual section of sl113.
cheers
Scott
