Dude I don’t know, all I can say is I had a spacer lift that preloaded the coil. It may be that the coilover (shown in picture) is adjusted way past the spring load threshold. I would NOT try to cram 285’s on if you are going to lower back to near stock or “level”
Does it have a lift on the rear?
If it doesn’t I would just level the truck and run a 265-275 max. Then you could at least unload some of that coil to lower it a little to lessen the angle on the cv.
Note: when and if you lower it, you’ll want to get the alignment checked. It’s recoomended to at least check it and obviously adjust if it’s way out.