I have a 91 12 valve, I bought it a few years back ans the speedo never worked, i never wad able to get it working either, i also juat put an NV4500 in it, need a diagram or some tricks

 

If you just need a speedo, you can use a GPS unit. Other that that, not sure.

Others will chime in.

 

you speedo is working by only a two wire sensor on the end of the transmission/transfer case. the White/orange wire is the signal and should go direct into your inst. cluster. The other wire is Dark blue and is a hard ground wire. if you have good ground and good wire to your cluster, the only other thing is either the sensor, the gear drive its screwed too, or the gear in your transmission.