It may be of interest to note that MB diesels are 21:1 or 22:1 compression ratio IDI -- I would investigate before I added propane. I am under the impression that the big V8s in american manufacture light trucks are mostly direct injection engines. Some use unit injectors (not the Cummins in the older Dodges, they use IDI with a VE pump). Much different application, usually have low rpm motors, too.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!