I suppose the person who can afford more than half a million dollars for a 113 based Mercedes hot rod doesn't wonder about value. I know Mechatronik does very good work, but I wish they would stop bastardizing these cars. The only thing worse than doing this to a 113 car is doing it to a 11, or, God forbid, a 300SL from the fifties. And both of those have been done.
All three series of cars drive perfectly well in their original conformation. Full disclosure- we installed a Getrag gearbox in my 280SL, but everything we did is completely reversible and we kept the original four-speed.