OK.. Here's the ABSOLUTE truth on the lower ball joints...
1) You CAN NOT buy these lower ball joints new, without buying the complete lower control arm. There is NO aftermarket supplier of the lower control arm and/or lower ball joint. Anyone you can buy the lower control arm from, it's the same part as if you bought it from the dealer.
2) You DO NOT have to replace the entire lower control arm assembly...
Ok. That's right; you don't have to replace the whole assembly. What you do have to do, though, is buy used lower control arms from a junkyard, or similiar.
To take out a ball joint, it extremely helps to have the control arm on your workbench. However, I've changed them on the truck before, so it can be done.
First thing you MUST do, is take a cutting wheel to the backside of the ball joint. These ball joints are press-fitted AND lock-nutted into place. The nut is jambed in place, by 4 metal tabs that have been bent over onto the nut. You need to cut these off, or you will mangle the threads of the nut when you remove it.
After the tabs are cut off, the nut will come off with only minor effort... I use an 18" pipe wrench. Comes off with ease...
Before you take the nut off completely, you need to get the ball joint out of the press fit... So when the nut is flush w/ the rear (all threads still in contact), take a mini-sledge, and start tapping, to press it out. It doesn't take a whole lot of effort, but it's not the easiest thing to do, either. Just be sure to hit it nice and solid, so it comes out, instead of just binds up.
Then take the nut off the rest of the way, and you're good to go.
To put the new ball joint in, you'll need to push it in as far as you can, into the lower control arm. I recommend putting in a washer before you put the nut back on. Yes, it's a big freaking washer, but if you don't do this, you're only making your life harder, and risking damage to the control arm...
Once the ball joint is in a little bit, put on the washer and the nut. Be sure to use some threadlock, because you no longer have the tabs that will hold the nut in place. Now tighten the nut on there. As you tighten it up, it will pull the ball joint into the press fitting. No need to worry about the ball joint rotating; it's shaped so that it can't. Just tighten it down ALL THE WAY, and you're good to go.
It's really not a hard change; the bulk of the work is either getting into a position to get to it, when it's on the truck, or taking the whole LCA off the truck. If you're keeping it on the truck, do yourself a favor, and take out the CV shaft, remove the shock, and remove the spindle from the lower control arm. The CV shaft is in the way of the nut; you can't take it off if the CV is installed. But, by leaving the control arm on the truck, you don't have to take off the t-bar, or the lower control arm bolts, so that saves a good bit of work right there.
If anybody needs a write-up/how-to, that's more in depth, I've got to replace one in the next few months; If requested, I can do a nice write-up w/ pictures, to show how to do it. It's really not hard; just time consuming.
One thing, though; don't waste your time trying to find new replacement BJ's... They don't exist. I've been to the Moog warehouse in town, and got to spend some quality time walking up and down their supply racks... There is NO aftermarket ball joint made on the market, like this one. Nobody else uses/makes a threaded AND press-fitted ball joint. So the only supply is low-mileage, used lower control arms. Get them whenever you can... These things aren't good for very long, if you're offroading.