If those heads aren't breathing much then they had to decrease the output in that Holley 750 carb so it's not running to potential either. You can lose a lot of HP if your carb isn't setup just right and you wouldn't really know it because your car will still drive on the road "ok". I've had it before and didn't know I was undersized in jetting and they were partially clogged. My car ran like a crack head runs from the cops after I had the carbs gone through.
Sounds like you have a fun weekend of tearing off the top end to at least inspect what you have or don't have.
Sounds like you have a fun weekend of tearing off the top end to at least inspect what you have or don't have.