Do these extensions require any drilling or modification to the bumper?

Fitment depends on your vehicle's original rear spat hole locations and fastener points. Reference your OEM bumper documentation or test-fit against the spat area before committing to fastener holes. Most installs use existing mounting points, but verification is key.

What surface prep should I do before painting?

Sand the surface with appropriate grit to achieve adhesion, then wipe clean of dust. Apply your chosen primer or paint system directly. FRP is compatible with standard automotive primers and urethane or enamel topcoats — follow your paint manufacturer's instructions for cure times and application.

Will these extensions sit flush with the original rear bumper?

The extensions are designed for the spat area and align with Type B styling intent. Gaps or fitment variance may occur depending on bumper condition and mounting angle. Test-fit before permanent fastening and adjust fastener positioning as needed to achieve the look you want.