Will this radiator fit both my automatic and manual transmission options?

Yes. This unit is engineered for both transmission types on this generation Mazda 6 — no separate part numbers needed.

Do I need a new radiator hose or thermostat housing when I install this?

The radiator mounts at factory points, but inspect your existing hoses and connections before install. Replace any that show cracking or deterioration.

What should I flush the cooling system with before installing the new radiator?

Drain the old coolant completely and rinse the system per your vehicle's service manual. Use the coolant type specified in your owner's documentation.