I will note that it seemed like your oil feed assembly that rides at the center of the rocker shafts seems to actually move and jump around (more up and down than side to side) and seemed there might have been some similar movement with the rocker shafts/stands.
To my knowledge those shouldn't be moving around and would suggest checking your rocker stand bolts to make sure everything is tight/secure and that your rocker shafts aren't actually moving (they could be badly worn which could account for movement in the stands). I noticed that movement too. It ain't right. Put on a glove and press on various places in the valve train while the engine is running to localize the noise. Press on both ends of each rocker arm as well. Can you "feel" the noise is one place more than others? Engine seems to be idling fast.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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