RW, I would first be pulling the motor down and find what locked it up. My only experience with diesel are engines much bigger than the tractor, "small" Blackstones through to Mirleese 16s around (24" diameter pistons). They all used cast iron but they also had interesting swirl pockets on the top of the pistons which I suspect would collapse or deform in aluminum . For a Tractor Pull (TP) I would be opting for cast iron, better metal-to-metal sliding characteristics, less expansion.
In that TP world I would assume you don't spend a lot of time getting the engine up to heat, with all the sliding parts working in harmony. It's probably a quick warm up and then full throttle for two minutes. Sounds a bit brutal on anything but the strongest of materials.
A call to the engine manufacturer would probably be more beneficial and enlightening.