it's quite possible to do a straight up 3.0L swap including heads, lower and upper intake manifolds...
many people (including me) have a funcitonal one
the only parts you have to use from a 2.5L are the motor mounts, timing cover, and exhaust manifolds.... using the heads and instakes from the 2.5L is an option other people use to get higher compression (and a few more ponies)
here are a bunch of pics of a full 3L engine being installed
http://atomicinternet.homeip.net/teamneco/puckpuck/showgallery.asp?galleryid=9
Nearly all suspension mods
Big ass stereo
...and more...
