98 Mazda Protege 1.5L Tappet Shims

[rljt60]

Engine runs fine with no smoke. But have click or clack noise. Engine has DOHC with tappets and shims for adjustment of valve lash. Stethoscope says loudest noise is from #3 cyl intake valves. Specs are .010" - .012" tapet shim to cam clearance. Most run from .016" - .018" but exhaust side of #3 has .022 clearance. I think I will replace all four shims for only #3 even though others are also out of tolerance by .004" to .006". Cams are ok.

How do you determine what size shim to get in a Mazda. Is there some kind of code that tells the installed shim's thickness?

Also, this is a "For Resale" car. What do you think of wisdom of only replacing #3 shims. Engine is quiet and has 100K.
Thanks,