Started my 340, IT KNOCKS! fresh rebuild HELP!!

I had something similar, windage tray was offset slightly, crank was hitting one side of the tray, sounded just like a rod knock, even increased with speed, as it would. Pulled the pan, removed the tray and could see 2 shiny spots where the crank was pounding, Bent the tray slightly, now all good.
Easy fix if that's the problem, good luck.