I'd remove all injectors, fill each cylinder with a cup of lube oil, then manually turn the engine 720 degrees (2 complete revolutions) to lubricate the bores and rings. Have the injectors pop tested at this point.

Check camshaft and crankshaft alignment marks, and valve clearances too. I would also open the side cover of the injection pump and check the pump's control rack for freedom of movement.

Then hook up a battery and crank the engine for a few seconds (without the injectors of course) to expell out all the oil in the cylinders.

Install the tested injectors with new compression heat steel gaskets, and start the engine.

Good luck, our prayers are with you.