I think the Limited and SRT6 use the same center support. I would use the after market Bilstein because it comes as a single complete unit. I think the only way you get the parts from Mercedes is in two pieces. The ball bearing is MB part 0089814325 and the rubber support is 1704100081. It is easier to work with something like the Bilstein ( I bought VAICO VC V30-7374) than messing with two separate parts and it is less expensive than buying Mercedes.
Be sure you also get the rubber boot to cover the splines MB# 202-411-04-97.
You can change the center support without removing the exhaust piping. A little tight, but that's the way i do it.