The 3.0/50 trim turbo will have to be clocked for the new environment. Since the turbine inlet will now point to the head rather than up, the center section will have to be clocked to align with the oil supply and drain fittings, and the compressor housing will have to be clocked to compensate. You'll have to swap over the slimmer wastegate housing of the 3.5/55 trim turbo to keep the 3.5/55 trim downpipe connector. That means modifying the 3.0/50 trim actuator as well. I don't know if the 3.0/50 trim downpipe connector can be made to fit so you don't have to modify the downpipe. None of the MB Garretts I've worked on have the turbo sections indexed so you might have to align things by trial-and-error, or use the 3.5/55 trim turbo as a guide to eyeball clocking.

My guess is the cylinder - piston crown and all - were steam cleaned by coolant seeping into the combustion chamber. Soot won't come off with a simple water or coolant soak.

Sixto
MB-less