I'd let it rip, I've done some ultra sketchy stuff. I've got a friend that strapped a VW tdi engine to the roofrack of his mk4 jetta from TX to NY.

Engine shouldn't be much heavier than a good sized bike, 5-600lbs according to google, if you can take any accessories off, and drain the oil.

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion