/6 has only four main bearings. And, it has a long stroke (OK) but with superlong skinny rods. Really bad for a diesel. If you want to make any sort of power, it is better to use a high quality engine as a base. Best is to use a designed diesel engine, although it is less of an experiment. I have had an Olds Diesel, which is a lowpressure engine, and it still blew headgaskets, even with studs for the heads. Went to M14 allen bolts, OK for a while, then I gave up and quit.
The 6.2 GM diesel can break the crank if you start it with start-gas, or if it has a leaky injector. A friend of mine broke the crank, without doing others than a normal start. He hated that car....
I would say a heavy, forged crank is a minimum for a diesel.
Please also think about what sort of combustion chamber to work with. A prechamber head from a /6 will require extensive mods, and is hard to make correctly.
What is your goal?
Thanks!