As for the 4.7L V8 I've had good and bad experiences with them. I have a 4.7 in my Ram and it's not a bad motor so far. It's pretty much bone stock. I just have over 41500 on it. At least it's been better to me than any 5.7L HEMI I've had. You can do a little bit more modding with the 4.7L in the earlier ones; 99-03 models. Those year on 4.7L responds well to a few mods like a Fastman Throttle Body, KRC 206 Cams, a better exhaust; 4.10 or 4.56 gears, and computer flash or Superchips. Now, if NZ is thinking about investing in a 4.7L there is two different versions. The first one is is just the base with usually 230-235 ponies and 295-300 torque. These can be found in 99-06 Jeep Grand Cherokees. Now the next version of the 4.7L V8 is HO which is pretty quick in the WJ platform Jeep. It is 265hp and 325 torque. It has a different set of cams, a hotter PCM, among with higher compression pistons, and some other things vs the standard 4.7L. To read more information regarding the 4.7L V8s and 4.0s you can read it here:
http://www.wjjeeps.com/engine.htm