What hardware do I need to mount these?

Mounting hardware and fastener specs are not detailed in the product data. You'll want to confirm your cab has factory mounting bosses or test-fit before deciding on adhesive versus mechanical fasteners.

Do these connect to the factory electrical, or do they need a new harness?

Wiring configuration isn't specified. Plan to verify whether they splice into existing cab lights or run independent power—your truck's wiring diagram will confirm the best route.

Can I return or exchange these if they don't fit?

Check ModSupply's return policy at checkout. Most aftermarket lights allow returns within a set window if unopened—just confirm the timeframe before ordering.