Your dad loves you and wants you to be safe. He feels that other drivers will see your turn intentions better with the turn lights where they are and I agree with him. Not every truck out there needs to be slick like a used bar of soap. Dare to be different. When my son got his first truck, I installed a full cage in it with 5-point belts, even though it was primarily a street truck, so I could feel better about him surviving an accident. Humor your dad and keep the lights where they are. Now go hug his neck and tell him that you love him for caring.