You'll need to make the parts from high carbon steel, then heat them to red for a certain length of time (1 hour per thickness of metal in inches), quench in oil or water (can be risky), then clean up and warm to the correct temperature to temper the metal to restore some toughness.
That's the gist of it, I can give proper details if you can't find any good guides.
Was thinking of touring car spares but ive heard thay didn't sell the blades separately and as im wanting to fit them to the rear of a mk1 fiesta i thought it may be easier to make from fresh.
cheers for the info its all helping the project slowly move on.