Do I need a new thermostat or water pump when I swap this radiator in?

Not necessarily. Radiator replacement is independent of those components. If your cooling system is otherwise healthy, the new radiator alone will restore function. If your thermostat or pump are already showing wear, now is a good time to address them while you have the system open.

Does this come with hose clamps or any fasteners?

Radiator assembly only — you'll reuse your existing hose clamps and upper/lower mounting bolts. Have those on hand before you start. If clamps are corroded or hard to loosen, grab new stainless steel clamps while you're at it.

Will I need to flush the cooling system before installing this?

Yes. Drain the old coolant completely and flush the block, hoses, and heater core to remove sediment and rust before the new radiator goes in. Old debris will clog a fresh radiator fast. Use distilled water for flushing, then refill with a 50/50 mix of coolant and water.