Yes, you can buy the new hardened 4th clutch hub. I know ZZP sells it, but you may be able to get it cheaper somewhere else.

As far as the rebuild kits go it can be done, but from what I've read there are some special tools needed to do it properly that add to the cost. If I have to do it again then I'm just going to pony up the $$ and get one from Dave at Triple Edge Performance so I won't have to replace it again in another 90K.