Transmission differentiation

[Mac Nibbles]

So I recently (stupidly) purchased a ka transmission without any sensors. I know there's a difference between the s13 ka dual and single cam transmissions, particularly the gear for the speed sensor. I know for sure I don't have a s14 transmission because there's no hole for the crank angle sensor. So my question is, how do I identify and tell the difference between the two types of s13 transmissions so I don't mistakenly cram the wrong speed sensor gear in there?

[Agamemnon]

All S13 manual speed sensors are the same.

[Mac Nibbles]

Apparently there are two possible different speed sensor pinion gears for the s13:
http://forums.nicoclub.com/240sx-speed-sensor-tutorial-t393740.html

Found some mixed info in this thread too:
http://forums.nicoclub.com/difference-between-ka24e-and-ka24de-trans-t283066.html

So some clarification would be appreciated

[Agamemnon]

The difference is that the one came with a 20 tooth pinion, and the "Sport pack" came with a 21 tooth pinion. The 21 tooth pinion was used to correct the speedometer due to changes in the diff gearing for faster acceleration. What diff are you using? If you have a lower geared diff or swapped in a JDM 180sx diff(4.36 ratio), then use the 12T pinion.

Really all you get is a 2-4mph difference in the speedo.