I covered the casting numbers out of the gate. There are only a couple of castings that are absolute which aren't identifiers for the 428. The water jackets also don't apply to earlier 428s. Sadly, many have been less than enchanted after purchasing a 428 to find it's a 390. Even the scratch doesn't absolutely guarantee a 428. The bore is about the only thing that is certain. What a conundrum, huh?