Will this radiator work with my existing Vega cooling hoses?

Depends on your hose diameter and connection ports. Test-fit the radiator inlet and outlet against your current hoses before committing—you may need adapter fittings or custom hose routing given the V8 swap configuration.

Do I need to buy a new water pump or thermostat for the V8 swap?

The radiator itself doesn't change those components—your V8 block will dictate water pump and thermostat size. Check your engine's specs separately.

What kind of coolant should I use, and does this need flushing before install?

Use whatever coolant your V8 engine requires—the radiator is compatible with standard automotive coolant. Before installing, flush it with distilled water to remove any manufacturing debris, then fill with fresh coolant.