Need to put this one to bed. So, some clues:
#2 was introduced with a different taillight. This taillight was an update that came some years later.
#3 was sold under more than one brand name, depending upon the country. Most were ravaged by the tinworm, and are long since gone.
#11 was a work vehicle.
#12 when considering what this might be, remember: these puzzle follow an order that must be followed
#17 is a well-known car, by a well-known designer. It's been a puzzle in its own right, as well.
#19 - A one-off show car
#20 - Strictly upper-crust.
