High-gain antenna placement

Run it in the headliner over to the pillar. Remove the pillar and run it down behind the pillar. Me

Where you install totally depends on the car. Since I work on a "time==keeping my job" basis, I generally find nooks and crannies under the dash. Were it my own car, I'd also consider: Behind the radio (especially on a truck!) In the center console. Beneath the back seats (have to extend a lot of wires-- make sure to use fairly thick gauge and solder connections). What you want: Nothing near moving parts! Wire tie stuff out of the way-- make sure you check the entire range of motion of anything that goes near your new wire. Don't extend the ignition wires if you're not very sure what you're doing. Mount the shock sensor somewhere reasonably firm and centrally located-- I like bracing struts if I can find them in reasonably places. If the antenna only goes so far, then that'll probably constrain you to putting it somewhere high in your dash...    Me