[Super Dude]

Well I don't see any damage on the spark plug, so it looks like someone installed it that way. With that said, anything is now possible. I have always gone over the valves with a new to me engine, or after a rebuild. I don't know how many I have found over tightened. You can gain engine vacuum if over tightened. Remove valve covers and watch rockers. Possible rocker noise could be from cam lobe wearing. After valves adjusted correctly, address timing, then carburetor. Not sure if your wires are in the correct position on the cap, can either move wires one position over or pull distributor and move a tooth to get vacuum advance in correct position. The carburetor should have a ported vacuum position for the advance line. Looks like it may be getting full vacuum if it was plugged into where your vacuum gauge is. I'm assuming you unplugged vac advance to check timing. A big cam engine will have some vacuum fluctuation, but most big cams I have had were 8-10 inches vacuum. After that is all in order, might have a four gas hooked up in tailpipe to see if 600 cfm is enough carb. I sure some others will chime in with more ideas. Good luck.