Well, yes. There were offices at the plants for that. You could also order at your local dealership then pick up the car at the assembly plant when it was done.

Orders are often mentioned as 'special' when they were just orders though.

A special order would be a car with a non-standard paint color or non-standard interior as two examples.

Regular orders would only be special to the person that ordered the car. I would guess 2-4 weeks for normal delivery from time of order from the 1970 paperwork on them that I have seen so far.