The urethane nose or bumper cover on my brother's 78 Z28 was distorted. The passenger front lower fender extension had suffered collision damage and had held the portion of the nose it was attached to "out-of-whack" for many years. We had the front of the car torn down for probably three or four years but the nose held that distorted shape, like it had a 'memory'. We ended up heating the area up with a heat gun and massaging the area back into shape. It didn't turn out perfect and required some filler. The end result was very good. I don't know if your filler is the same material. If you do use a heat gun go slow. We watched the temperature of the material with an infrared thermometer and it still snuck up on us. The material gets to a certain temperature and then suddenly becomes elastic.
Is that filler available (reproduced)? If so, then at least you have an option if the repair goes badly. If you do try the heat gun approach, I would do it with the piece on the car. Hope this helps.