IMHO, here are the relevant facts I've gleaned:

The 617 turbo engine has a chain driven high output oil pump to drive the oil jets. The non-turbo engine doesn't have the jets, doesn't have the oil holes in the pistons, and a few other odds and ends. The non-turbo oil pump is driven off the IP.

Piston pins are larger in the turbo, bore is different (smaller or larger, depending upon exact engine), but the crank is the same.

I don't think MB "beefed up" the lower end -- I suspect it was originally stressed for a turbo, as the development engine (the C111 test car) was turbocharged at more than one atmosphere!

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!