Will this mirror stay stable at highway speeds with a loaded trailer?

Manual mirrors are solid once mounted — no power electronics to rattle. Vibration depends on how tight you bolt it down and whether the mounting points are clean and prepped. Check fastener torque after your first few towing trips.

Does this use factory mounting holes or do I need to drill?

This assembly mounts at factory points — no drilling needed. Test-fit before final tightening to confirm alignment with your truck's door and fender.

Will the mirror head clear the truck bed or cab when fully extended?

Mounting method and exact clearance not confirmed — you'll need to mock it up or measure the extension against your specific bed height and cab configuration before final install.