Mark,
The condition of my 6.9 when purchased was less than desirable.
I feel I have poured money into it to make it a far more desirable vehicle than what it was.
In my view, when someone will come to buy my
690SEL, he or she will not be too worried about the speedo as they would have seen all the documented work carried out (new front and rear end -incl discs, etc- total rust removal, new dash, new sunroof, new paint, newer interior with no tears, etc, etc..)
But when someone buys a car , plays with the speedo and tries a quick resell, then you are playing with fire.
On another note, there was a time when these cars were used daily and were no longer new enough to have money spent on.
I can imagine the speedo stopping and the owner checking with his local wrecker only to find no such thing as a 260km/h speedo, but a 240km/h one that will fit and, according to the mechanic and wrecker, will do the job.