I have both engines in and I would say that they are both fairly easy to tune up. I have found however that my 4.0 like to go through plugs quicker than most.
I would go with Plugs (NKG), Wires (high perf 8mm), "HOT" coil (not neccesary, but you can gap plugs wider), Cap (any quality brand), Rotor (any), Air filter (I like the K&N cold air system), Change all fluids (eng, trans, t-case, axles, anti-freeze flush), New thermastat (cooler range will give more power but slightly worse fuel mileage), Check hoses (If spongy then replace both rad. and heater hoses, don't forget the short hoses by water pump), If belts are overly cracked then replace (belts- cracks running same direction as grooves are bad, less than 10 cracks per inch the other way is acceptable but I would replace), Check front end for any slop, ect.
This is how I treat my vehicles and I have het to be left stranded and I drive about 25,000/year on road and many hours off road as well.
DON'T FORGET- Replace muffler bearings with a high performance chromoly set and grease regularly as well as keeping headlight fluid full and clean!