A spun bearing does not automatically mean the crank is junk or the block is junk.
A friend of mine has an IH with a 466 engine. The drain plug came out and he caught it quickly. Resulted in a main bearing being spun. He took it to the dealer and the dealer said several thousand dollars to fix the problem.
The friend ask for me to take a look at the situation. I saw no significant damage to the crank or the bearing cap and thought maybe the block might also be okay. I suggested he get an opinion from a local independent mechanic.
Bottom line, the independent mechanic agreed with me. He used emery cloth on the crank and rolled in a new main bearing. Five years later, the engine is still running fine.
Take a close look at the crank and bearing cap and don't assume like the dealer mechanic did. Let me know specifically what you see regarding the crank and the bearing cap.