That I can' t help you with.
They use these things called "Nutzerts" to create threaded mounting locations in the frame. They are essentially giant rivets that are threaded in the middle. You seat them with a couple wrenches and a bolt designed to squeeze them down so that the tip mushrooms inside the frame. You can then bolt into them as if the frame were threaded in that location. Once they are seated, they can never be removed (short of drilling them out of the frame).
My skid package came complete with the required Nutzerts and tools. I recall that someone tried to do a swap similar to yours and had some problems locating the Nutzerts. I think the parts themselves are not all that uncommon, it is finding the right sized ones for the Jeep. Dealers were no help to that guy, as they just gave him a blank stare.
This thread might be helpful:
http://www.jeepsunlimited.com/forums/sh ... p?t=132285
Also, you can buy the parts online here to (just not with the Jeep part #):
http://store.nutsandbolts.com/nutserts- ... uveco.html