Difference between 6cyl and 4cyl instrument cluster

What is the difference between an instrument cluster for a 4cyl and a 6 cyl?
I am looking for a replacement instrument cluster (mine doesnt have a tach). Someone on eb@y is selling one for a 6 cyl (I have a 4cyl). They look the same. What difference does it make what engine they are for???
Maybe the tach is calibrated differently for the 6 cyl? Any ideas???

What I want:



What I have:

 

All the ones I've seen on 01 and up are identical to mine. If anything's different it's internal and I have no idea.

 

I believe the 4 cylinder double cabs came with the tach. But the others did not.

 

Mine's got a tach. I think it came with SR5, but not sure.

 

I have a feeling its more of a trim package thing (SR5/TRD have tach and base model doesn't), or something like that. Just a complete guess though since this seems to be the pattern with other manufacturers. Some other features not available to the non-tach are the digital odometer and trip meters as well. Could be seen as an upgrade.

 

My stock 1998 TRD SR5 3.4L v6 has the tach.

 

I am primarily concerned with the 1995-97 Tacomas. They do not have the digital odometer and there were no Double Cabs.
Can anyone tell me why the one out of a 6cyl will not work in my 4cyl?

 

Different number of cylinders = different number of signals / pulses per engine cycle. The clusters' integrated circuit boards are hard-wired for either 4 or 6 cylinders, so you definitely need to find a replacement cluster from a Taco with the same number of cylinders as yours. The difference is in the circuit boards, not in the tach itself.