The standard Benz bolt pattern is 112/5, and this hasn't changed in at least four decades, so don't worry about that. Instead, you should worry about wheel offset and width.
As a starting point, any 7" wheel with an offset greater than 44 (the original standard offset for the 124) may not fit
(the rim may fit physically, but the tire mounted on it will rub the front shock if it were wider than 195.)
As a rule of thumb, if you plan fit a wheel that's wider than 7", you should make sure it has LESS offset by at least half the amount of the added width.
Example: If you wanna fit an 8" wide rim, the offset should not be more than 30mm (ET30), but ET35 will do if the wheel was 16".