Eric.
I would love to see pictures of your car
Since my original above request I did spend some time on the follow site
http://mercedes.heckflosse.nl/I found the follow information
In 1969 there were a total of 2501 2.8's and 176 3.5's built
In 1970 there were a total of 613 2.8's and 3300 3.5's built
In 1971 there were a total of 68 2.8's and 1026 3.5's built
Of the above information it does not separate coupes from cabriolets. Nor does the 1969 production numbers of 2501 2.8's separate out low and high grille cars. One can only assume that if they made only 176 3.5's in 1969 that the number of low grill 2.8's was even less.
I'm fairly certain there were a far low number of low grille 2.8's than there were 3.5's mainly because most buyers were willing to spend the extra money of the V8 option.