Components production

How will be handled car components production?
For example, actually engine is fully specified, but for components like gearbox suspension and so on there is no specification available…
A gearbox may differ from another, it may cost less or can handle more torque, actually this things are threated as quality slider, but if I have a car company probably I have 3-4 gearbox ( more torque, less gear, automatic, sequential etc… ) and I need to produce or at last buy it in some way…
This speech may be applied to other components like suspension and driver assist ( probably is a good idea to buy it externally in order to simplify the game ).
In this manner will be possible to make different car with the same components and not only engine.