The dash was changed from a painted to black crackle finish at the start of 1974 MY (August 1973), so the last painted dash would be a July 1973 build.
But the last body colour dash would be July 1969, from 1970 MY (August 1969) the dash would be painted black.
All US/Canadian buses had the M511 padded dash option, which was available as an extra cost option for LHD buses in the rest of the world as well.