You can have a custon bar built that can be shaped to fit stock interior, fi you plan to race the car the rule book will have specifics that cannot be altered , if you just want the bar for stiffness , you can customize the bar to fit your needs . For example NHRA requries that the door bars are high enough to be within 6" of your shoulder & must be welded to 6" square plates bolted through the floor , other rule books like SCCA , Ralley , Nascar all vary how the bar needs to be built & what material is used etc