Where is a good place to ground an amp in reg cab 99 f150?

 

I like to drill a small (3/16") hole in a seat bracket. Put a bolt through it and put the eye connector for your ground wire on this bolt.

Later, if you add amps, you have an easy point to ground.

Lots of people use the seat mounting bolt itself, but it's not a good idea. Those bolts should be tight, and it's hard to do so without twisting up your ground wire.

 

^^^ seat bracket or if you have to remove the jack you can use the screw hole where the jack was mounted. Or you can lift the carpet/rubber mat and secure the ground wire to the floor of the truck.