I'm not 100% convinced that the pic of the turbo M100 is from this car, since I can't identify any key chassis components in the pic. I can confirm that the engine was a 6,8 with a listed bore of 107mm, stroke of 95mm and capacity of 6834cm3. Oh and I managed to find some more clarity (!) with a better pic of the engine fitted in the SLC prototype. Definitely NOT a SL, a 5,0L or even a M117. It clearly shows a M100 V1, likely to be the original 6,8 and probably sourced from the killed-off-by-regs W109 campaign! Apparently 550hp.
It looks like that car survives today which makes it rather significant since it seems all of the W109s and other AMG race cars from that era are long gone...
I find it highly unlikely they added turbos to the car & later removed them in favour of the aftermarket stacks. More likely something that was planned but never undertaken. I’d say their focus moved the the M117 & DOHC versions.