I have the 560Sl and am looking to replace stock wheels, what did you have available?
Sorry, but I don't have two wheels that will fit the front of a 560sl (without spacers) right now.
Tomorrow I will have six gold BBS RS, two of which could be made to fit a 560sl with spacer/adapters.
If you were willing to use spacers with the r129 EVO1 8x16 et34 wheels on the front of your 560sl, you could do that. Those look similar to Lorinser LO wheels (16" 15-hole, same basic design, but EVO1 have angles in the spokes while LOs are flat).
Any of the wheels I own would fit on the back of a 560sl though.
I already sold the two BBS RS133 wheels I had which were designed for the front of a 560sl. They didn't last very long.
AMG Aero1 wheels will fit a 560sl (including front wheels), and Gen2 Pentas also fit. I am not sure about AMG OZ 3-piece.
There is no measurement that I am aware of that you can request as a specification to determine if the wheels would fit a 560sl. So it's a matter of either knowing what you are doing, or buying a wheel that you know will fit.
If you are interested in running spacers, let me know. PM/email me.