"It has an original 1968 400 block that has been refreshed..."
"You're running an 11 bolt pump, make sure all the correct parts are in there."
I think HO is correct. At some point, your timing cover, water pump, and possibly the pullies have been "updated". Not a bad thing at all. Just makes it a bit more challenging to put together the right parts.
I'm a hobbyist. Not a professional. Don't be hatin'!