I have a 1997 ford ranger ext. cab. I cant find a place to ground my amp. everywhere i have tryed didn't work. It needs to be within three feet of the back cab. thanks for the help.

Sheet metal cutting screw through the floorpan would be the likely choice, given the circumstances.

Good Luck

Or you could ground it at the rear seat anchor bolt.

use a self tapping screw the size of the ring terminal on your grounding wire, attach your driver to your drill and ram it through the floor with a washer between the carpet and the terminal.