Here is a writeup showing how the ROKMEN Frame Tie Ins attach to the TJ frames.
Perhaps you can get an idea from this to use on your frame tie in. Basically two different length of bolts are used for the frame...
a longer 4 1/2" bolt for the upper hole in the frame, this bolt goes clear through to the other side of the frame.
a shorter 2 1/2" bolt for the lower hole in the frame, this bolt is inserted from he inside of the frame and the nut goes on the outside. See the writeup and photos for it to make more sense.
You shouldn't have to move the tank, I don't think it is possible anyway