Can you see through the pushrods out of #8, or can you run a piece of safety wire through them unrestricted? I'd still drain the oil and check for metal. If you wiped a lobe that's a bunch of microscopic abrasive flowing through the engine, so you're looking at a total teardown. I wouldn't waste a nickel on building a flat tappet cam engine today. It's been said that it's not "IF" it will fail, but only "When" it will fail.

If you didn't wipe a lobe? It's a pretty healthy knock from the video, so chances are you're gonna be taking it down, at least enough to get #8 pulled out....