Hello,
In vehicle manager you may add new type for select list field with help language file.
{yours site}/components/com_vehiclemanager/language/english.php
please check constants:
_VEHICLE_MANAGER_OPTION_NUMBER_OF_CYLINDERS
_VEHICLE_MANAGER_OPTION_VEHICLE_TYPE
For change models and markers or add self in Vehicle manager please check file:
{yours site}/administrator/components/com_vehiclemanager/makers_and_models.txt
thanks,
OrdaSoft team