Didn't see this post until just now!!
http://www.fbirides.com/assets/files/install_files/260215.pdf
That's the newer instructions- I think they should answer most of your questions.The sending units install between the lift valve and the airbag at each corner- of course, the tank sender installs in the tank!We have T fittings for your valves that have an 1/8" port machined into them for the sending unit, or you can just T into the line from the valves to the bags for the sender.
Let me know if you have any other questions!
-Phil at FBI