Just guessing and trying to be logical, I suspect the brake pads are the same for the CLK430 and the E430. In my mind, these are identical except for 2 doors vs. 4 doors. Most, if not all, of the 4matics have different front end parts and so those might differ.
An easy way to check, in the comfort of your own home, would be to compare part numbers on some online MB parts site. You could also get the info for free by calling some MB dealer's parts department and asking them.
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