When you checked out the pushrods...did you happen to inspect the tips of the them? I had a similar ticking noise that turned into a knocking noise. I finally ripped it all apart and it ended up being a pushrod wasn't getting adequate lubrication due to a piece of gasket to RTV silicone. It was jammed into the hollow, center part of the pushrod where the oil travels up to lube where the rocker pivots on the top of the push rod. So the pushrod & rocker were not getting any lubrication really, at all. I replaced the scratched up pushrod, readjusted the valves...and everything has been a-ok.
