Here's what I've installed in the truck's interior:

-Escalade instrument cluster
-In-dash radar detector with outside temperature readout
-ScanGauge OBD-II display and trip computer
-Alpine CDA-9855 head unit with XM radio receiver and iPod integration
-Alpine "Type X" 6.5" component speakers hidden in front doors
-Kenwood KSC-SW1 powered subwoofer under back seat
-DEI alarm/remote start system, very well hidden

Here are some pictures: