Rear end alignment issue 1969 cuda

Pretty sure heating them up hot enough to bend the steel easily enough, would alter the metallurgy of the spring steel and would do "bad things". Get a new set from Buy Quality Automotive Leaf Springs, Coil Springs and Suspension Parts for your Classic or Antique Auto and be done with it. They are good and relatively cheap to get the right set of springs under your car.
I bought ss springs from summit racing November 2017 Arlington texas brand new 105.00 each. Had them in stock.