Does this radiator include the transmission cooler lines?

The radiator assembly includes the integrated transmission oil cooler. Check your existing lines — they may be reusable, or source lines separately if yours are cracked or corroded.

Will I need a new thermostat or flush the system before installing?

A full coolant flush is smart practice before dropping in a new radiator. Thermostat replacement isn't required unless it's already failing — test it first or replace it while you're in there if you want peace of mind.

Does this come with hose clamps or coolant hoses?

Just the radiator. You'll reuse your existing hoses and clamps unless they're damaged. If anything looks cracked or bulging, swap those out at the same time.