I have the K357 kit sitting in my garage, it's going on my 99 this spring. it comes with 3 boxes. I noticed the only difference in part numbers between the 3 boxes in the 357 kit and the 358 kit is the box with the steering knuckle box. Honestly, I don't know if they are interchangeable between kits. I've spent alot of time looking through my kit boxes, but haven't had a chance to compare anything the kits for the newer ones.
If you haven't already, get ahold of Shane B. on here. He knows a lot more than i do.
OR go here, lots of good information there.