I'm curious what your plans are. Are you going to get rid of the body lift and replace it with the IFS lift? Also, are you going to keep the 36" tires or go with something smaller/bigger?

If you plan to combine the 3" body lift with a 4" IFS lift, I wouldn't recommend it. Tall trucks are dangerous, especially tall IFS trucks, because the suspension has little to no compression on the trail and your that much more likely to flip over if you're top heavy.

If you're going to keep running 36s, then a 4" IFS kit may not be a bad idea, especially if you are going to ditch the body lift. If you need more clearance, you can do a little fender trimming to make up the difference. You shouldn't need much.

If you were running 33" tires or smaller, I'd recommend not even bothering with a 4" IFS lift or even body lift and just adding some add-a-leaf and/or longer shackles in the rear and upper ball joint spacers for the front, but you'll need more to clear 36s.

As far as IFS kits go, I would absolute go with a kit that uses one piece drop brackets. I believe the Superlift kits have these as well as Trailmaster, but don't quote me. The multiple piece bracket kits sometimes have alignment problems and come loose.

Good luck.