So, the KJ-based Nitro gets a 260hp 4.0 V6 as its optional engine. I'd like 260hp! Its just bored/stroked so it wouldnt be any heavier or physically larger. I bet the engine mounts are the same. And they put that engine in front of the same transmissions (I think) so I bet this would be a pretty straightfoward swap. Heres an info page (they list different HP than the dodge site)
http://www.allpar.com/mopar/38-40.html
I dont think that they sell the 4.0 as a crate engine...nor do I have the knowledge, money, or time to pull of that swap. But that would be badass to have something like an H.O. option for our KJs!
::EDIT::
Turns out I was wrong, the 4.0 is a derivative of the 3.5 V6. But still, if its going in a vehicle as similar to the Liberty as the Nitro it would probably still be a straightforward swap.