I think the confusion here may be that the reference materials say the block casting number is for a 1961 413, but the ID stampings do not match anything from 1961. It could be that the block was cast in 1961, and the stamps on the ID pad are just wrong. It could also be that the reference materials are incomplete, and the casting number could have been used in 1959 and 1960 as well as 1961.
If the casting number is correct, the engine is a 1961. If the stamping is correct, it is from a 1959 300E. It wouldn’t be the first time reference materials for casting numbers was wrong or incomplete, so I’ m leaning toward this being a 1959 300E engine.