I've seen panels with etch coat, and panels with epoxy coat. Etch coat has to be sealed to keep it from rusting. The epoxy coated ones would be fine for "ready to install", but I would still strip the outside of the panel to bare metal cause I've seen it "chip" off in flakes. Also, depending on the color of the car, you may want an even coverage of color. Spend the money now and do it right the first time.