Do these work with my truck's factory wiring harness?

Yes. These use factory mounting points and connect to your existing wiring without adapters or rewiring.

Will the smoked lens reduce brake light brightness?

The tint darkens the appearance, but smoked tail lights are street-legal. If visibility in low light is a concern, test-fit during dusk before finalizing your install.

Do I need bulbs, or are they pre-installed?

Bulb inclusion is not confirmed — plan to reuse your existing bulbs or source replacements before install to avoid downtime.