Thanks for the reply.
If anything, when I go to 7G 722.9 Trans I may need a Higher / Taller Diff ratio than the (non standard) 2.87 which I have in the car right now.
Initially I will leave the 2.87 and see what I think of it
if I find that the 7G's lower 1st Cog ratio is useless then I'll likely have to drop to something around 2.65, but bearing in mind this is a Sports Car not a Tourer I will have to carefully consider once I've driven it with a 7G / 2.87 combo
It does have 18" Wheels, can't really get anything larger under the R170's rear Inner Wheel-arches due to the Vario Roof mechanism constraints upon the Wheel Tubs, I did look at the feasibilty of "tubbing" an R170 when I fitted new Rear Wheelarches and rebuilt the inners on my other Silver V6 SLK320 car.
Diff wise, the factory SLK 320 comes with a 3.27 ratio, which is way too low geared for the V8 Motor, the factory V8 cars came with a much larger cased 2.82 diff, which won't fit R170 platform rear Subframes.
My easiest option was either a 3.07 (SLK 32 AMG / Crossfire SRT - 6) Diff, which proved to be un-obtanium in UK, so I used a 2.87 Diff from an earlier pre facelift Diesel W203 C Class, that again is a straight swap into an R170 / Crossfire Subframe. The 2.87 proved to be a perfect guesstimate with this Car / Engine and Trans Combo.
The main reason I didn't buy LSD yet is in case I need to swap to another Diff, (which would likely be a bigger Casing and CWP), so couldn't then be swapped over.
Transmission wise I'm currently using the (higher) Torque Rated 722.6 (5 speed) V8 & V12 Transmission that came from the same Donor car (2002 W220 S500) that the V8 Engine and the Brake Calipers came from.
The 7G Tronic Trans I have is a 722.9
01 which was originally fitted to V8 W220 S class / V8 R230 SL / V8 W211 E Class 5.0 Cars.
My 722.901 originally came from an R230 SL500, and is fitted with a VGS 2 Plate (TCU is internal on a 7G), but as mentioned above it has a customised SCN altered to suit the Cars Diff, Tyre Sizes, all 4 Modes and AMG Shift programming.