A strange project indeed. Euro headlights as per 1967 and before, these were never seen on a 6.3... Electrical air compressor ?!? The original compressor seems to still sit on the engine.
Anyway the car can still be rescued if someone wants to put in some effort. Stick shift can be fun but 6-speed seems rather idiotic given the M100 torque characteristics.
Says Ingvar, 300SEL 6.3 #74
109.018.12 1968 Bronze Braun (M100 in good shape)
126.039.1A 1988 Dunkelblau (M117 so a bit slower)
+ A few other MBs used for daily transport