Do these mount directly to factory locations, or do I need to modify anything?

These bolt straight to factory mounting points—no drilling, no brackets, no chassis work. You're using the same fasteners your OEM lights used.

Are the bulbs and wiring harness included with these housings?

Housings only. You'll transfer your existing bulbs and harness from your stock headlights over to these units.

Will the chrome housing resist pitting and corrosion over time?

Chrome finish holds up well against UV and moisture, but like any exposed chrome it can spot if not wiped dry regularly. Interior construction is sealed to protect internal components from humidity.