The rear speakers are powered by an existing amp in the trunk, only the speaker wires are attached and the speaker housings are in the wooded deck and not separately grounded. The amp housing is grounded. Should the speaker frames be grounded?

The antenna is a Hirschmann universal type. I used two of the existing wires: power all the time (red); and the wire that provided power when the radio was on and antenna switch in "up" position. The antenna had a ground wire that was isolated from the large inner tube and coax coupling nut (they were common). I needed to ground that part of the antenna unit, as well as the ground wire from the antenna "box" for the radio and antenna to work. So I think the antenna is well grounded. Thanks for the assistance!