Using the older ones is fine. Good in fact. The puzzle is why number 6 intake. Did the foot come clear off, or just break the plastic clip?
Paul
It's pretty common to have them broken. Most people don't even know it, until they take the rockers off for some reason. The pieces of plastic can only go back to the oil pan, but most of the time they stay in the head.
Paul
Have you checked to see if the pushrod is bent and maybe side loading it a little?