having kept many of those check valves over the years "just because", after looking for them, they must be in a "safe place", because i can't find them ! [gee, imagine that !
]
however, after saying that, your valve looks like some i have pulled from mid to late 70's C-body's.
unfortunately, as i can't find my stash of those valves, i can not confirm the cast in lettering as being a factory part.
so just consider this as a bump, so others with more brains than i possess can confirm or not your part is a factory item.
