Does this mount at the factory holes, or do I need to drill?

This uses factory mounting points — no drilling. Bolt directly to your existing towing mirror location with the fasteners your F-150 originally came with.

Will the mirror stability hold up at highway speeds?

Manual mirrors are solid once locked in position. The key is tightening the adjustment bolts firmly and checking them before towing — loose fasteners cause vibration, not the mirror design itself.

What hardware do I need to install this?

Use the fasteners from your truck's original towing mirror or equivalent bolts that fit the factory holes. Torque specs and sizing depend on your specific model year — check your truck's service manual or ask your dealer for the correct hardware before starting.