Thanks DR-Kiev. Am I right in assuming that the 5th wire connects controller ground to HD ground?
In fact this SATA "pinout" is relatively straightforward to determine. You don't need to be an Einstein or a "guru" to work it out.
All you need to look for are two thin parallel pairs of traces, probably capacitively coupled, running between the bridge chip and the MCU. These will be the Tx/Rx pairs.
As for the order of the pins, one would expect that the physical positions of the pins on the bridge chip and the MCU would be in the same order as the SATA connector on a SATA HD. This would facilitate an orderly PCB layout (imagine a SATA connector intercepting the Tx/Rx pairs). If this doesn't work, then you would try the reverse order, for those cases where the chips are on the reverse side of the board. If neither works, then there are still 6 additional permutations.
One other concern would be whether simply tapping into the SATA traces creates a double termination. Even removing the coupling capacitors would still leave reflective stubs. Whether this significantly impairs data communications would be something to consider. Still one more concern would be whether the bridge could be held in the reset state, to keep it quiet during data transfers.
As for the 12-pin header, einstein's statement that "there is a special pinout connection for this drive which can be done and converted to sata" was ambiguous in that it suggested he had gained SATA access via the header. AFAICT from the available photos, there are no thin parallel traces terminating at the header, so SATA access is unlikely.
However, in another thread, I observed a trace from pin 6 of the bridge's EEPROM chip heading out to the header, after passing through a series resistor, R97. Although R97 was not populated, it appeared, in the absence of a clearer photo, that the header provided access to the EEPROM, or to the bridge.
In retrospect, it also makes sense that the SATA test points are consecutively numbered.