The SLK32 is a complete
AMG update that touches all major components of the car, it is not practical or cost effective to try to convert a 320 to an SLK32, there are just too many changes to engine, cooling, brakes, trans, diff, ABS, ECUs, etc. (Just buy an SLK32, they aren't that expensive)
However - the suspension conversion could be done to update the 320 (or 230) to the SLK32 version relatively easily.
Control arms and linkages are the same.
Parts that are different:
SLK32 has factory Eibach springs front and rear, these can be installed on the 320
SLK32 has larger anti roll bars f/r, which can be installed on the 320
SLK32 has 20% higher damping rates on front shocks, rear shocks the same on 320
The factory shocks for front of the '32 may be discontinued, and would be quite expensive anyway.
A better solution is to use Bilstein B6 on the front and B4 on the rear, this would be very OEM and similar damping as the factory '32 setup.
Another alternative would be to use Koni sport yellow adjustable shocks f/r if you really want to get into suspension tuning, a bit more money though,
Just the shocks would be a big difference, try the B6/B4 trick and see if that satisfies before doing springs and roll bars (which probably have to be sourced used).
ALSO - The Bilstein part catalog has an apparent error, in that they don't recognize the difference in SLK32/320/230 and show the same part numbers for all 3 models - so if you order all 4 shocks B6, they will be right in the front for a '32 but too firm in the rear, and conversely B4 will be too soft in front and same in rear. SO, the Bilstein solution to mimic the factory '32 is B6 front and B4 rear.
Happy top down spirited motoring,
R