Here's a good "old" thread on the subject.
https://www.crossfireforum.org/forum...ht=gear+ratios
I actually purchased my Crossfire with every intention of getting a 3.73:1 gear for it. That was until I found this forum almost 6 months later and discovered it really wasn't possible to simply go to your local Mercedes dealer and just order a ring and pinion.
It's true, You would need a set of good "drag radials" to make use of a new gear at the track, but with the usual "other" mods available, I have no doubts SRT6's would be running in the 11's all the time.
With the right gear, even a NA car might see 13's (but it would probably take something like a 4.56:1 to do it)