Seems that the owner of this engine is confused or not sure what he has. If it is for a 250S then it is a carbureted M108 engine. A M129 engine is fuel injected and unique to a 250SE or 250SL. It can't be both. If it is truly a M129 engine and is a factory new short block, then it could be a very good deal since just the new piston assemblies are worth about 2K these days. However I would start with a M130 2.8 liter engine instead of this 2.5 liter when building a "race pagoda".