Careful with the offset if purchasing alloys - I had a slight disagreement with the guy at the wheel place when purchasing my new replicas. He swore that he had been fitting alloys to Merc 190Es for 15 years and knew all about it.
I showed him my owner's manual and he freaked out (after having told me that my car had been lowered at one stage, had been modified, etc.).....
In my 190e manual/book I have the original wheels listed in the
technical specifications section with an ET number of 49 for the 6 x 15 and ET number of 42 for the 7 x 15.