Do these use the factory mounting holes?

Yes. These mount at factory side marker locations on the front bumper — no drilling or fabrication needed. Just bolt them in place using existing hardware points.

Is the smoke finish sealed, or will it yellow over time?

Mounting method and long-term durability specs not confirmed — test-fit first and assess the lens quality before committing to permanent install. If yellowing is a concern, UV-protective clear coating can help.

Will these work with my bumper if I've already modified it?

These are cut for factory bumper geometry. If your bumper has been heavily reshaped or swapped, test-fit before purchase to confirm fitment.