As background, I’m the second owner of my Chevelle and have full maintenance records from the late previous/original owner. Both those and my experiences pulling the intake today indicate that this is the first time the engine has been opened up.
I spent all day (minus the time for three trips to the store and half an hour to eat lunch) swapping the new intake in. Upon removing the old (remarkably heavy) intake, I made a discovery.
Why yes, that is the top third-ish of a broken pushrod. None of mine are broken, none look to have been replaced, and all the maintenance records and what I saw today indicate that this engine has never been opened up.
Upon close inspection, you can see where it bent and failed (very hard/brittle). I guess now I can tell people my car came with 16 1/3 pushrods from the factory...
(Yes I cleaned up the crap that fell in when I pulled the intake before closing it up. I don’t think my shop vac liked it).
As a bonus, here’s today’s progress. Need to pick up a fitting for the vacuum port on the rear and figure out how to make the upper alternator bracket work (it misses the hole by like 1/4").