Sorry when I typed "JY" I was meaning "junkyard". Was typing fast and just shorted it.
Any 4.0L block you can start with...doesn't have to any perticular model ANY 4.0L block will work doesn't matter if the block is from a YJ / TJ cherokee or grand cherokee. The block is all the same.
As for what to look for...well newer is always better...and well one that isn't cracked.