Ideas on what's causing my click/tick/rattle noise?

I had a tick in my 74's slant that increased/decreased with rpm that I couldn't chase down for the life of me... It was driving me insane. It turned out to be the oil dipstick. My kid shut the hood on my dipstick, snapping it right on the "F" in "full" and never told me.... And put it back... So it was springing up and brushing against the crank or something I guess... Pull the stick, no noise... Put it back, noise... The dumbest f'n thing right... But that's what it was... So worth a look...

On my 75 I also have a "tick" and that is from an exhaust valve not seating correctly... When the car is idling put your hand or a piece of paper over/near the tailpipe... If you feel or see sucking back into the exhaust the valve isn't seating or is bad...