I agree that only the facts matter, and the Pontiac Parts Manual is pretty hard to argue with.
It was not my intention to foster hearsay as opposed to facts when I said the valvetrain is different. While I didn't look up the parts, I did have it from a pretty reliable source- JimC2002, who had mentioned a few times in these forums that GM advised him to use straight 30 weight to avoid clacking at cold startup- specifically because of his 400HO engine. (Jim's Post) I was pretty sure I had heard someone else mention the springs and lifters were different, but if the part numbers are the same, I agree that that should remain the record unless or until documentation can prove otherwise.