Did you assemble the engine, or purchase as a long/short block (or crate) ? I've seen engines where the shop forgot to replace the gallery plugs at either end of the block after they were removed for cleanup/tanking. It can happen -
The time you've spent priming is certainly enough to get flow through the cam galleries and pushrods in my opinion. I've used gearless distributor housings to pre-oil before, I use a dedicated pre-oiler since many years ago. Try another oiler (inexpensive compared to a teardown) !
Certainly concerning -
Steve