The change in the form of government shall take place on the first Monday in November following the date of the next ensuing municipal election for the election of members of the governing body held by the municipality during a general municipal election year as established by Section 11-46-21, except in Class 6 cities wherein the municipal governing body has elected to have a nine-member council as authorized in Section 11-43A-8; and in such cities the change in the form of government may take place on the first Monday in November in any even-numbered year, designated therefor by the municipal governing body unless the election approving such change was held in 1983, in which case the change shall take place on the first Monday in October 1986.