I used a "Retro-Sound" unit in my panel truck. It fits right in the stock holes.
They have adjustable on/off - tuning controls that allow you to precisely
mount them. They have a face plate that is made for the AD trucks for a slight additional charge. I have it attached to a 600 watt amp with 5 speakers, although
the unit puts out plenty of power to drive speakers on its own.
Sounds terrific & has a little black attachment so you can plug in a USB drive.
I use my iPod mostly …. plugs right in.
I like their stuff and would recommend.