first off... is the dual zone sensor a shock sensor or a motion sensor? if its motion, then putting it behind the dash anywhere is a bad location. in fact, even if its a shock sensor, some random location behind the dash isnt the best place to put it.
motion sensor - mount as close to the center of your cab as possible. inside the armrest/under the center seat will work.
shock sensor - mount on a SOLID surface. there's a security module behind the floor cupholders that is attached to a bracket thats welded/rivited to the truck body. under or around that bracket is perfect.
EDIT: looks like its a shock sensor included with that kit. i have no idea what the window is for, as shock sensors dont need light or anything. maybe its just a window to make it look cool, or to provide access to lights on the unit or something.
*SOLD 05/24/08* 2003 Silver Frost XLT 4 Door, 3.0 v6 4x2 Automatic.
255/60 Toyo Proxes S/T on 18 x 9 Boss 304 Chrome Wheels.
Slotted Rotors with Ferro-Carbon pads.
Volant CAI, Crane Roller Rockers, Borla Pro XS Exhaust, MSD DIS-4 Plus Ignition.
Kenwood Headunit w/7" Screen, Infinity Kappas in front and rear, 12" JL Sub,
Custom Ported Enclosure with Flushmounted Infinity Amps.
Custom Interior including Reupholstered Headliner and 7" Visor-mounted LCD Screens.