I went with a slightly different approach on creating the car bases. I have created each part, left them in containers based on what part they are. Then I can select what parts I want and duplicate them and put them into their own container to be modified after the fact. I also made a weaponless car top that extends the full length of the four wheeled car. I think the users of the vehicle would like to see out the back window without having to look through the weapon.
With the Three Wheel Objects:
With the Four Wheel Objects:
