I third that valves and seats notion. I have two 64 352 4barrels at home. One runs one doesn't (due to the fact its in my garage in boxes). The 352 I tore down had most likely 180K on her and the seats were starting to pit and the stems and guides were loose on a few. I even had one valve that had mushroomed at the top and was impossible to remove without some professional help. Also, it looked as if someone tried running synthetic oil in her which clogged the crap out of it making it impossible for the oil to drain out of the top of the head. Just some of my probs. Let us know what you find