67 Lifter problem

[Khazer]

I bought a 67 mustang 302 awhile back and when we bought it they said it has a lifter problem and we went and looked at the Rocker arms and pushrods and that all seems fine but what would make the rattling noise that its making its also on both sides under the valve covers. and how tight are the rocker arms suposed to be, should you be able to wiggle the pushrod because we put them tight and when we start it up they loosen up so u can move em a little, same with the rocker arms. Any help would be appreciated.