Car Bodywork CAD Model

I need a CAD model for the exterior bodywork of a 2007 Mazda MX-5 NC Soft Top, intended for the production of aftermarket body parts. The model should be detailed with surface features and provided in STEP format. I have a .obj file of a scan of an existing one of these cars but I have been unable to convert it into any format I can use due to the file size being 1.8GB.

Requirements:
- Accurate dimensions and detailed surface features
- Delivered in STEP format
- Experience in automotive CAD design
- Proficiency in CAD software

Ideal Skills:
- Automotive engineering knowledge
- Attention to detail
- Strong CAD modeling skills