We drilled the mounting points using a 5/16" drill bit.
The drivers side mounting holes are very close to the exhaust system, so be careful. If you have aftermarket exhaust on your rig, you may have to do a little 'massaging' to get around it. If the installer followed the stock exhaust path you won't have any problem at all. We then removed the crossmember and scribed some lines to follow with the sawzall. Make sure you locate the cut lines at least 3/4" to the inside of the mounting holes that were just drilled. You need enough 'meat' for the new crossmember to hold onto. When cutting the crossmember you will realize just how flimsy the stock unit is. The new component is quite a bit stronger. Be sure you cut to the inside of the holes... Don't cut off the new mounting points you just drilled or you will be dragging out the welder! We then moved to the inside of the cab to make a place for the new shifter to come through. There is a good template that is included with the instructions. Just line up the template as instructed and mark the corners of the new hole. We just used a metal punch to to mark them. You can use a sabre saw or sawzall to cut out the small hole in the tunnel. We decided to use the cutoff wheel to make the cuts with more precision. Time to fill the case with oil. Trail Tough recommends GL-5 type 90 weight gear oil.
The Rock Block goes up into the space where the jack shaft had once been. The ends look exactly like the ends on the jack shaft, so slide the splined fitting into the back of the transmission and bolt the rear flange to the transfer case.