Tapping sound - lifters? Rockers?

[turbopowered68]

i am having a annoying tapping sound.
could it be the rockers?
When the valve is in the closed position is there suppose to be any clearance between the rocker and the valve?
i also have a few lifters that bleed out really fast, What can/should i do about this? new lifters? leave it alone?
Maybe not having any pre-load on the lifters is causing the bleed out?
Also how do i pre-load the the valves that are loose? New rockers? Longer push rods?
thanks for your help

Stock long block 165K Miles