What I did to pick out the rotors is look at the stock rotors on bremboparts site. They have very detailed diagram of all the measurements so then I tried to get the same hat as stock crossfire but instead of 300, I needed 360mm.
I tried to get clever and fit slk 55 amg p030 360mm front rotors (Brembo 09.9547.33) but with 8 piston caliper, the inner pegs of the caliper contact the hat.

front rotors from slk 55 p030 did not work


these are 8 piston front calipers and 4 piston rear calipers. Take a look at image labeled "front rotor comparison top" and you can see all 4 pistons on one side.
6 piston caliper is easier to mount since I hear the bolts are same M12 instead of m14 for the 8 piston version, but I dont have any experience with 6 piston calipers to be sure.

One thing I read somewhere is if you dont use all the calipers from the same system then your brakes might not distribute the braking as designed and create a larger bias than originally designed. I'm no expert to know the actual effects, but maybe something to think about.

I read up spacers can create extra load on the bearings especially with a swapped engine/calipers/rotors extra weight. I might end up with spacers but would be my last choice. Was looking at larger 19/20 inch rims from another AMG model but hard to say if those would clear