I'm trying to find a ground location in my 02 F-150 extended cab around 3 feet from my backseat. I cannot find an obvious place where I can ground something out at and I was wondering if anyone knew a good spot in the back of the cab??

 

A simple place where an amp was grounded in my supercab by whoever owned it, was one of the mounting bolts for the rear seat.

 

I have my amps grounded to the sheetmetal under the door sill trim panels, its a good place to run wires. Just use some grease to keep the rust out.