I have that #14 head on my 87 SDL also, educated speculation puts the car at 300-400k mi, most of which it was neglected. It runs quite well with catchup maintainance and doesnt over heat. I assume that someday I will have the issue but it has a helluva lot of use on it so far. I have read some pretty mixed stuff but so far so good. Im keeping an eye out for a cheap score on a better head so I have it if/when I need it.

__________________
87 300SDL (Silver/red)
08 VW GTI (Sold)
89 F250 5sp turbo diesel
00 Triumph Sprint ST (4sale)
00 Polaris Xplorer 400 4x4
09 Kawi KLR