Coil springs on a 4x4 gmt-400 would be DIFFICULT to say the least. As to adjustments to ride height, they must be made with the front tires off the ground. Any weight on the front tires, and you can snap the adjusting bolts. I'll try and go on my laptop later, and post the directions for how to adjust ride height. It's not a preset number of turns or anything like that. You have to jave it on level ground, take a level, and you have to measure the difference between 2 defined reference points. As a starting point though, you want it adjusted so that your cv axles are not level, but so that the outer axle is about 1-1.5 inches lower than the inner. Or adjust it so that the ball joints are centered in there sockets at ride height.
Which ball joints are you having trouble with?