https://www.wiringspecialties.com/s13katrha.html
You can't find it anymore because there are 2 groups of Nissan owners. Those who can read through the FSM and don't need to ask, and the other who just hit up W.S. for a $125 plug and play harness.
FWIW $125 isn't a bad deal. The previous owner of your car sold you a half baked swap. Good thing for you, if the tranny is in and the clutch pedal/master cylinder installed, the hard work is done at least.
Also the speed sensors are different between the S13/S14 transmissions. Good to make sure you have the correct one for your application;
Picture of an S13 speed sensor ^
Picture of S14 speed sensor ^
Picture of the sub-harness courtesy of the FSM. Note the difference between the S13/S14 speed sensor. S13 has a long pigtail to connect up there.
Not kidding. That thing is hella long;
