Well, if you want to make it easy for yourself, you could create ranked templates based on difficulty upgrades and setback dice. Something like:
Archaic X: Upgrade the difficulty of all skill checks to operate, repair or maintain the vehicle X times.
Prototype X: Downgrade the difficulty of all skill checks to operate the vehicle X times and upgrade the difficulty to repair or maintain the vehicle X times. A despair result may be used to cause a critical hit to the vehicle, adding +X x10 to the roll.
Junker X: Add X setback dice to all skill checks to operate, repair or maintain the vehicle X times. To reduce a vehicle's rank of Junker one step costs X x10% of the vehicles base cost in credits and requires a mechanics check with a difficulty of X.