Will this bolt straight onto my truck without modification?

Yes. This assembly uses factory mounting points—no drilling, cutting, or adapter brackets needed. Install like you would remove the original halogen unit.

Do I need to replace the wiring harness?

No. This is a direct electrical swap. Plug it into the existing harness and you're done. LED draw is lower than halogen, so your truck's electrical system handles it fine.

Is this just the left light, or does it come as a pair?

This is the left side only. If you want matching tail lights, order the right side separately—they're sold individually.