Q: I cant find specific laws on modifying vehicles.

I have looked through my states laws online and checked my states DMV for any related questions or answers with either no results or pages upon pages of results not relating to my question. I live in the state of Nebraska and would like to know what laws are involved in modifying my cars outward and interior appearance, for example; cutting and shaping sheet metal on the outside of the vehicle in which it does not have the same likeness or apperance in which it had before. (Hood scoops, wider wheel wells, convertable modifications, exhaust reshaping, underglow and all around apperance changing modifications.) as well as interior apperance changes such as; changes to the dashboard, seats center console without disrupting safety of airbags and other equipment. My question is; what can I legally modify on my car and what process would I need to take to license it if it looks nothing like the original? Thank you for your time and I appreciate any and all answers.