This is a very interesting thread. I didn't see any answers regarding whether a V8 conversion would work with a manual car. I assume the engine bolt pattern is the same for both automatics and manuals. The biggest problem I see is to find a flywheel to bolt onto the Mercedes V8. As far as I know, Mercedes does not offer a manual transmission behind their V8. Can the V6 flywheel be adapted to the V8? Does anyone make a generic balanced flywheel that can be drilled for the Mercedes crankshaft?

Once the flywheel issue has been solved, the biggest problem I see is to remove the crankshaft and have it machined to accept a pilot bearing.

This thread may not be the proper place, but has anyone swaped in a Mercedes 3.5 liter v6 from a 350 model? These have 268-306HP. That may be an easy swap for almost SRT-6 power.