I am in the process of redoing my audio setup, keeping the same marine boat speakers, just moving locations, they would fit in the dash, technically, but I can't imagine mounting speakers into a Bronco dash would sound very good. The thin metal dash would likely vibrate and rattle. Not to mention there is not much room. I would think kick panel enclosures under the dash (I have those) or probably even better sound would be from an easy custom under dash center hump enclosure type set up that some here have done.
I never have a top or doors on, and it pop-up showers in low country SC all the time, so I use marine grade radios/speakers. I actually recently found a water resistant slim-fit subwoofer that fits under the front passenger seat. I have test fitted it, and it will fit completely under the seat and be protected from the elements and reasonably from theft. I can't say how it sounds yet, but it is from Pyle, so it's somewhat name brand and is ruggederized with metal screen and hard plastic outer.
