If it were me and I wanted to cruise more comfortably and didn't mind sacrificing acceleration (what little there is to begin with), I would be willing with my own money to try a 346 rear from the 300d na. I think you could get away with that.

Its about a 6.7% OD from the stock. It will probably allow you a 75 mph cruising speed or maybe 77.

The euro 240s were offered with the five speed which has about 17% od top gear and I think they did not change the rear end when they put that in so I think this probably would work.

The payback in fuel economy would be long though. If you drove 30,000 a year thats 1000 gallons at 30 mpg (optomistic but easy to calculate). At 4 per gal that is 4,000. A 5% (this might be reasonalbe to assume and its easy to calculate) savings in fuel would be 200 per year, so if you hire the work done it would take 2 or 3 years to pay back.

My 83 240 with 300d na euro motor running a 307 rear end will do 30 highway and 20 town. The gear is a little tall taking off but if you are patient its not a problem.

Tom W

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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.