Thank You for the information.
As for welding the Block. I have welded a few Large Marine Diesel & Steam powerplants in my day.
To do the job right the engine needs disasembled.
Pre-heat Block & control the cooling after welded. On top of this is the price of that 99%nickel rod. Point is if this was a $5000-100,000 + engine block. It might justfy the cost.
As for your friends larg farm tractor Diesel.
It was a good idea to try to weld it. Any Diesel is not cheap.