S14 cluster problems
 

My S14 is from the states, so it had an American cluster in MPH, which I needed to replace. The cluster itself had problems, IE, no illumination, the speedo needle pulsed up and down while driving, never staying in one spot, and it read too high. I've swapped in a JDM Zenki cluster, and it works great, except for the fact that the speedo needle reads twice as high. I've done some research and found out there could be several problems:

-The sensor could be reading incorrectly
-The sensor gear is for an automatic (Both the M/T & A/T gears have 20 teeth, but the A/T one is slightly different with little splines on it)
-My transmission could be from an S13 (Previous owner did the 5 speed swap and S13 and S14 speedo assemblies don't mesh nicely)
-I'm not sure if there are different M/T sensors that read in MPH or KM's
-I perhaps have an S13 sensor in my S14 tranny

If someone could clarify if the A/T and M/T sensors are the same, but the pinion gears on them are just different that would be great. Even better, if someone else has encountered this problem and they fixed it, if they could explain what it may be to save me the headache and I could fix it myself, that would be great. I can't seem to get right down to the exact answer to my issue.