I also question the statement that non-detergent oil should be used. Today's oil is a lot more technologically advanced than the oil that was originally used in these trucks. I think modern oil will help extend the life of these truck engines. I for one am not going to follow the instructions in the owners manual that says I should add kerosene to the oil in winter!
The main bearings were inserts, not babbit, at least in my 49. I am not sure of 46 models.
