Hi Jake,
It crosses under the frame rails at the rear of the front wheel wells. A couple of pics in post #11 show it a little bit. The only problem is has caused so far is that when I installed the new brake hard lines, the line that crosses from driver to pass side and connects to the rear line was designed to transition from the back side of the front cross member to the inside of the pass frame rail. In that location the brake line would be laying against the exhaust pipe because of the exhaust routing. I had to do some rework to re-route that brake line to keep it away from the exhaust.
I don't expect clearance problems with my setup, because the truck was dropped before (cut coil springs), and the drop spindles/drop coils are not going to drop it that much more. (although, I could be wrong!)
This pic shows ground clearance before I started this current drop project.
Let me know if you want to see more pics of that area.
Jon