Stock Rocker arms clearances and fit

Guys,
I am running stock rocker arm assemblies and have a persistent lifter "tick" that seems to be getting worse on my mid-70s 360LA in a 74 duster. Engine was "rebuilt" by P.O. and everything looks really clean under the valve covers. Tick is only on Driver side and I have previously pulled/inspected/measured all the lifters and push-rods on that head. They look "nearly new" and the push-rods are all the same length w ~zero wear. So,....not being familiar with these stock rocker arm assemblies, I am entertaining just purchasing a replacement set (probably fm Mancini) and swapping them out since I can find no other "smoking gun" reasons for the "tick."
My QUESTION: Is there any spec on the max amount of cold clearance that should exist btwn the intake & exhaust rocker arms & valve ends on these stamped rockers? OR...Is there any sort of rule of thumb as to how loose the rockers should fit/rotate on the shaft? A few of mine are loose enough be able to grab and rock back and forth a little when they are unloaded. What I mean is that, a few "feel" like there is about .010-.020" of gap between the shaft and the holes through the rocker arms. At the same time, others have a much closer (by feel) tolerance fit on the shaft. (The surface condition of the rocker arms and shaft looks really good with no signs of any previous rust damage etc....)
NOTE: I plan to pull the heads over the winter or next Spring and have them inspected/ "re-worked" or maybe upgrade to Aluminum, so I don't want to invest in a full set of rollers/adjustable rockers at this time. I really just want to get rid of the tick while I drive the car for the next few months.

THX-Scott