If any Mercedes engine left the factory with a perfectly neutral balance on the flywheel it was just shear luck and I wouldn't bet on finding one. As detailed in the service manual the engines are balanced as an assembly with the two balancing planes being the balancer and the flywheel.

I have had these balanced by a local shop and they had no trouble doing it. They do alot of racing engines and such so they are used to out of the box stuff. The key is probably finding a shop used to doing out of the ordinary stuff.

__________________
1993 300D 2.5 Turbo (blue/ blue tex)
1991 350SDL (White/ Gray leather)
1983 300TD Turbo 5-speed manual (Green/ Beige)
1985 300SD (Black/ Black Leather)
1985 300TD (White/ Green Tex)
1980 300SD (Astral Silver/ Black Leather)
1990 560SEL (White/ Gray Leather)
1993 300SD (Black/ Black Leather)
1967 200D (Green/ Beige Tex)
1969 300SEL 6.3 (Moss Green Metallic/ Green Leather)
1975 300D (Astral Silver/ Green Tex)
2001 Ford Excursion Diesel