Brian,
All 1968-69 300 Deluxe models have a single post, see picture.
1970 Chevelle 300 Deluxe model would be the ONLY 1970 Chevelle model.....to have them. Possibly the Nomad or Greenbiar Wagon too. It`s a base line option.
Rainer, you out there? You would know for certain.
http://www.cuepics.com/maurice/
Dan