I would start with a JY core that turns over, blocks hardly ever show any significant wear, cranks show almost no wear even with lack of oil changes and other abuse the bearings usually take the abuse, they seem to be faily soft. Timing chains, guides, tensioners are terrible in these things. That will save you money on boring and buying pistons, throw in rings and bearings maybe deck the block and thats all I would do to the bottom end. If you do feel the need to do a set of pistons you might as well get the domed ones for the HO engine, you get more power and MPG with no down side. The top end should get new lifters as they like to loosen up and let the rockers fall off. Re surface the heads. Get the brand new timing chain, tensioner and gears set off fleabay. Re assemble.

If you need a few extra HP you can add the HO cams. I am not a fan as I like low speed TQ and the 4.7 needs all the help it can get but they are not too bad and you can feel the increase.

If your looking at core engines you can get one of the HO engines (easy to identify as there is a big "HO" cast into the head in the valley near the front of the head), even the earlier ones bolt in if you swap your tone wheels while the cam and crank are out. The HO has bigger cams, dome pistons, floating rods and forged crank (not that I have ever seen a cast crank cause a problem). Some of the earlier ones had supposedly better intakes but you need to make sure you get one that has your matching EGR system or lack of it to keep it emmisions legal. If you dont have EGR you can use EGR engine parts and just block off the unused holes but it is harder to go the other way.

If you were not 3000 miles away I would pull the motor out of my 07 dakota I just did all that to and sell it and you could bolt it in and go, I need a good reason to stick my 6.4 BGE in it.