My best luck with killing tapping noises from lifters (which is usually the cause of tapping from 4.0's) is Seafoam engine treatment in the crank case. I replace 1/4 of the engine oil with seafoam, up to a max of 1L, and go drive it for 20-30 minutes. Then with everything nice and hot (and crap is suspended in the oil) I change the oil and filter.
Oil weight, 10w30 in the summer, 5w30 in the winter, but you'll get a lot of opinions on that. That's what I run. A good tune up (plugs, wires, cap and rotor, coil if needed, set timing) will provide max power and fuel efficiency. Proper maintenance, oil changes and air filters will provide maximum life.
'91 Frankenheep YJ. 4.0, 4" BDS, Richmond 8.8, Titan 12k, 35" KM2's, rust.
'88 YJ, 4.2/4.0 head, +4½" & shackles, BFG 33's (sold)