i did this a while back, thought i would post a mini write-up for anyone that might be planning to do it.
make sure you use jackstands and do everything safely and don't blame me if anything goes wrong...
first, disconnect one link of the rear sway-bar (if you have one still), this makes it easier to articulate the axle with the jack.
use spring compressors to squeeze the coil down enough that you can get it off the bump-stop. i used the jack to first squeeze the coil a lot, so i didnt' have to run the spring compressors down manually except the last few turns, then let the jack back down.
pray that the cheap harbor freight spring compressors don't break. lay the coil out of the way, never let it point at your body/head.
drill as straight as you can up into the bump-stop hit plate. i used a 27/64" bit, worked for me. thre is a dimple in the center of the plate already, so the drill will self-center. i bought a cheap right-angle ryobi drill since i already had some other ryobi tools/batteries/chargers. the metal is fairly thin and will drill fast. the right-angle drill comes in handy for other things like mounting rock-rails.
tap the hole using a 7/16" - 14 (coarse) tap. again i just used a cheap harbor frieght tap & die set, but it worked fine for this. just remember that the tap's are hardened and therefore brittle, so don't put any side stress on them. if you brake it off in there, you will have a hell of a time drilling it out. move in a few threads at a time, then back out a couple turns and then back in.
here is the IRO bump-stop extension, i put the mounting bolt inside it, then taped over the end to keep the bolt from falling out as i dropped the whole package into the coil later.
here is the coil back on the perch, with the extension and mounting bolt dropped into the spring. i went ahead and put some threadlock on the threads of the bolt just before i dropped all this back in. the allen wrench needed is a 3/8".
again i used the jack to squeeze the coil and take most pressure off the spring compressors. loosen the last little bit of tension from the compressors, then remove them.
let the jack and axle down as far as you can, so that there is a large amount of space between each coil turn. then you can get your fingers into the coil enough to turn the extension and bolt to get it started. then you may have to raise the axle just a little to find a good point at which your allen wrench will fit between a space in the coil. tighten it up good!
rinse and repeat for the other side, put your sway-bar link back on, wheels/tires, and you're done.