I used to have a 90 300CE and the brakes, at least the calipers as I remember, were different, being 4 piston. My application books are all in my office (I'm at home now)
so measure your rotor dimensions, thickness and diameter, to be sure of interchange.
Porsche used slotted rotors on all the 928s and had no problems as they are less prone to cracking as drilled and still serve the purpose of releasing gas buildup between the rotor and brake pad. I've slotted my own for my 190/5.0 on my milling machine using a ball end mill to my own pattern...no problem.
300SE, 300CE, 190/5.0