Do these mount at the factory attachment points?

Yes—these bolt into the existing mounting locations on your 579 cab. No drilling or bracket fabrication required.

What about wiring—do I need a new harness?

These units are designed to accept standard plug connectors. Verify your truck's existing connector type before ordering; adapter harnesses are widely available if needed.

Do the LEDs ever need replacing, or is the whole assembly done once they fail?

LED modules are sealed into the assembly. When they reach end of life, you'll replace the entire headlight unit rather than swap individual bulbs.