Here's a good link:
http://en.wikipedia.org/wiki/Nikasil
Most 2.4L 175 and all 200hp 2.4L 200 were chrome bore motors. There were a few steel sleeve 2.4L like the 150 XR4 and a 175 Ski special. I've seen many 2.4L rebuilt with 1 or 2 sleeves that run fine. These 2.4L engines are tough motors.
Chrome and Nikasil offers several advantages over steel which is why you find them in most race motors and airplane engines. Some of the advantages are
Better heat transfer.
Better lubricating surface.
Tighter tolerances.
Chrome is much harder than steel resulting in less wear to the cylinder walls.
Depending on the year the 2.0L blocks are the same as 2.4L or 2.5L blocks. They are just sleeved down to 2.0L with a thick thick steel sleeve . . . which is why they weigh more (20lbs or so) than the 2.4L or 2.5L motors. 2.0L are also pretty tough if you lose a piston, then they can be bored over easily.
Both motors can be bought for $1500 or so. 2.4L motors need to have at least 120psi when you test compression.
if you get one of these motors you must remove the oil injection and spark advance/idle stabilizer module if you want it to live.
If you can find a clean freshwater 25" motor . . . buy it!!