Do these bolt straight to the factory frame, or do I need to modify the rocker panel?

They mount at factory rocker points with no drilling or cutting required. Use your existing bolt holes and you're done.

Will the matte finish hold up to mud and trail spray?

Matte black hides dirt well and resists water spotting better than gloss. Rinse regularly like any exterior trim and you'll keep the finish looking sharp.

What hardware do I need to install these?

Confirm bolt sizes and torque specs with your JL service manual before ordering fasteners separately. Factory fastener holes are pre-drilled and ready to accept standard metric hardware.