A five speed would be the ultimate as Barry says. I agree with him too that you dont want to go taller than the 347 gears in a 240d.

Back when a 240 was my primary car I tended to keep it at no higher than 72 mph on the highway. Faster just seemed too frantic.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.