I agree if an engine swap is desired a good candidate would be the 500E motor from an 84 mercedes. The engine is robust and simple to run and maintain. The injection is completely mechanical so computer problems are not a factor.

I had an 84 500SEC which I ran about 50,000 miles in three years. I found the 500 motor to be comparable to the 300D on maintenance but it did use a lot more fuel, never really breaking 20 mpg at any speed. But it also would not break a sweat running 85 on the highway if you didn't mind paying for fuel at 13 mpg.

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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.