I have the same yr and 2.5 engine and its my DD. so I just did a combo lift (springs/shocks) add 1.2 BL w/ MML. That allows me to run 33s with good clearance and I didn't have to spend $$$ on the full Monty. If you want a 6" I guess you are planning on 35-37s? I would do a long arm and you'll have to re-gear it, new axels, etc. I'm not sure what you want to do: crawl or mud. I would repost your question on the TJ tech section. You'll have quick answers, this is above my pay grade. I know the 98 2.5L has 4.10 gears which is sweet if your staying below 35s.