Ok so the top sensor on the LH side of the Trans is the Backup switch. The NSS or Clutch switch (Depending on what book you are looking at) is on or behind the clutch petal arm under the dash. This is what Alldata states as far as testing.
This switch functions magnetically. Do not use magnetized tools near this switch.
1. If the switch is open when the clutch pedal is released, speed control will not operate. This must be corrected before making any other tests. Use only a voltmeter of 5000 ohm/volt rating or higher when performing the clutch switch test.
2. Disconnect switch pigtail connector from speed control harness connector, then connect an ohmmeter to the two switch connector terminals.
3. With clutch pedal in the fully released position, the resistance should be less than 5 ohms. With clutch pedal fully depressed, the circuit should be open.
4. If switch does not function as described, remove and replace switch.
I was going crazy because depending on what book or reference you are looking at it is called something different. But seems the part is reference to the clutch switch, which will throw a 67. As far as the code 15 I would clear the codes and try again. I am not sure about using that computer with the swap, since I have not done that before, or if it is the cause of the 67, but hopefully this helps a little. I wouldn't think the 67 would throw the MIL, but maybe so.