They aren't suitable because the offset of the wheel is wrong for the CLK.
The SL or CL has a much bigger offset than yours which is why they are sticking out past the fender.
Spacers will only make it worse and make the wheel stick out further still.
Spacers are for wheels that have too small an offset for that particular vehicle and thus bring the wheel back out inline with where the OEM one would have sat.
OP, look on the back of your old wheels and look for the double digit number with the designation ET (ET45) for example.
Then see what the AMG ones are.
To illustrate how this works and what ET you can get away with check this site out. Custom rims, wheel tire packages for your ride - RIMSnTIRES.com