Several cars have received later Mercedes V8s (M117 4.5) or modern five/six-speed conversions to improve driveability and cruising RPM. Purists dock value for non-original drivetrains, but owners who have done it report dramatic improvements in refinement over the original four-speed automatic.
Engine and gearbox swaps: divisive but sometimes excellent
Mercedes-Benz W111 Coupe / Cabriolet · mechanical