It would be good to post the details of what you have already, and your expectations for performance, such as range, acceleration, and top speed. Also details of the motor and VFD to see if it is appropriate for the specifications. You could also figure out the mechanical details of mounting the motor in the vehicle and connecting to the drivetrain. You could even hook up the VFD and run the car a short distance using mains AC power and an extension cord. The batteries and charger will likely be the most expensive and critical components.