Knock and smoke

That doesn't look like piston. Anti freeze in pan=intake or head, usually intake. the pieces are too curved to be piston, and it wouldn't have ran that good. The smoke looked like your leaky valve cover; loose plugs, oil in threads, oil burning off header.

5 qts?, didn't look like out the exhaust. no inked stamping would be left on a piston. Old alum rocker arm stuck in head?

Going to watch vids again.