I have converted 2 turbo US car to manual shift. One of them is the US 300D turbo car that wolfwalker mentioned driving. I have had 2 factory stick 300D's and have never noticed a difference in how much the rev's drop between shift between them and my converted cars. All Mercedes IP's are only governed at idle and full speed, so I don't see the effect that the governor would have on rev drop.

The 300D flywheel is significantly heavier than the 240D flywheel and much much heavier than the 280 (M110) flywheel.

No Mercedes flywheel is neutral balanced, if you don't believe me just have it spun on a balancing machine. They are far from neutral balanced. There is a very specific procedure in the manual in balancing the flywheel when it is being replaced. I have never done it without balancing the flywheel to match the automatic flywheel coming off, but I have seem some jobs that it wasn't done and they were always chasing vibrations. One vehicle couldn't run a week without breaking the air filter mounts. The flywheels should be marked before they are removed, I have noticed some later cars are marked with paint from the factory. Good luck finding that in 20 years. They got cheaper and cheaper with how they located the flywheels. In the 60's they had dowel pins, 70's they had good chisel type marks, and as I mentioned I have seen some from the 80's that were marked with paint if you can find it.

On all 300D's with factory stickshifts there is a rubber damper mounted right behind the flex disc, some US 300SD's had this too for some reason. Without this damper you will get a resonance at about 2000 RPM's under load.

I have some euro 300D flywheels that I brought back in a suit case from Belgium that I could part with if someone is interested in doing it right.

On fuel economy, my 300TD with the 3.07 rear axle I have gotten as high as 33 MPG on the highway, which is only impressive if you see how I drive. The turbo engine pulls very nicely in 5th gear on the interstate, even through the mountains I haven't had to downshift, just set the cruise and go. Pulling hills in first gear can be a challenge because of the high axle ratio, it puts the engine below where the turbo can give you any help.

I don't think that the stick conversion makes the car faster from 0-60 because you lose some boost between shifts, but it is nice to be able to burn rubber in an old diesel.

Matt

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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