OK, here's what I remember and believe to be true...
Bolt pattern for Mercedes 1960 - probably forever is 5 x 112. This bolt pattern is also used for some VW / Audi cars including a Vanagon I think. Probably lots of VW cars but I doubt that will help since the offset is going to be completely wrong for the FWD setups.
Offset: 30 mm positive for a 1967ish Mercedes.
110/111 cars came with 5.5 x 13" rims.
108, 109, 113, 114, 115, 116, 123 came with 14" rims, except in some non-US markets where they came with 15" steel rims.
108, 109, 113, 114, 115, 116, 123 came with 5.5" and 6" width rims depending on the application. For instance, a 1980 W123 240 D in 1980 is going to have 14 x 5.5 rims, as is a 1971 W114 250 C, but a 1967 W113 250 SL is going to have 14 x 6" rims. All of the wheels are interchangable, it's a question of what size tires you are using and if you need the wider rim. A 30 mm positive offset is going to be pretty much correct for all of these.
The 14" wheels with 30 mm offset can be used on the earlier cars with the 13" rims and makes a great upgrade, particularly for something like a 190 SL.
I'm fairly sure that a W126 has an entirely different offset and that you can't use those rims.
You can find more info on the older Mercedes wheels here:
Pagoda SL Group Technical Manual :: WheelsTires / Start
And if you want to buy aluminum wheels that take the full wheel cover and weigh 11 pounds, you can contact me.