If I'm not mistaken hotrods have been subject to headlight height regulations at times meaning they had to be a certain distance from the the road. But this would have had a direct effect on placement of the headlamps. I know fenders have been an issue off and on with some states also. I know twenty five years ago Iowa had bumper and headlamp hieght laws for pickups. The DOT had a minamum and maximum hieght for each model, where they went who knows.