I have an 04 xterra. the 3.3L V6 is 145 cu in. I have a chance to grab a 2001 dodge ram 5.9L V8 (360 cu in.) for cheap. can it fit? can it be modified to fit in my Xterra?

With enough money and skill yes it could, but it would cost a fortune. would you be looking at this as a trail rig, or a DD?

Oh, yeah, it'll fit no problem. I've seen, like, at least 30 of those swaps done.

Kidding of course. Nobody knows, it's never been done. You're in uncharted territory. Good luck and such, but we're not holding our breath on an "I did it!" post from you in a year or so.

Also, you don't modify the engine (and transmission and transfer case) to fit the Xterra, you have to modify the Xterra (extensively) to fit the engine and such.