retrofitting skids?

I have a ('93 XJ, 4x4, 4.0L, auto, 231.)
My XJ didn't come with skids. I just acquired some from the pull-a-part.
I picked up all the hardware and the front skid will go in swimmingly.
The sub-frame and tranny cross member has the holes for the skid and I have the bolts, but there is no captive nuts in the holes on the cross or sub?
what should i do?
thanks

You either need to get the nut strips. or use matching washers/nuts

You can either use nutserts if you want to curse yourself while trying to take the skids off for maintenance, or you can just get matching washers/nuts like Johnnie said. Hardware could be metric, if you can't find 9.8 or 10.9 class metric hardware locally just use the nearest size grade-8 SAE fasteners. If you have trouble holding the nuts in place inside the crossmember/frame try welding a piece of heavy steel wire to them to use as a handle.