I went with a 3.4l when my 3.0l died. But you say you have a good running 3.0l, if you are set on swapping the motor i would gather what you need and just run that 3.0l till it blows up.
If I were you I would regear first just like snow toy recommended. See how you like it then. I will tell you, even with the 3.4l I am was not super happy when I had stock gears in the axle. Thinking back when I had a 3.0l I would bump the timing a little above spec, I believe that made a little differnce. My buddy has headers on his 3.0l and it cruises along on the highway just fine with stock gears and 37's.
