Haven't seen those numbers myself, but try here: https://www.v8buick.com/index.php?threads/400-430-455-block-id-prep-and-oiling-mods.214613/
Post pics of the engines. Maybe those are Nailhead casting numbers? EDIT: 1364705 is a 64-65 401/425 nailhead Here's some casting number charts to help with your decoding.