Are 6.9's now the most common W116's that now survive?
It wouldn't be much of a surprise to me, because they were so special in the first place, and have always well worth preserving and to be looked after well, to defend yourself against high restoration costs.
According to Mercedes-Benz information that I remember, about 260 of them were sold in Australia, (mostly 1978 and 1979 build), and I guess that perhaps 100 or so are still in road going condition.
That would be a reasonably high survival rate.
Special cars deserve special attention.