I order the whole kit from a local shop, $148

 

I thought that was only for electronic tachs ???

 

Your probably correct. I didn't even know that they had mechanical tachs in the late '90s.

 

It is only for electronic gauges. Surely yours has this?

 

I don't think mine has electronic gauges check this pic:

 

I'll be damned, you are probably right. I dont know exactly how to fix the speedo error then. I know my dad has a 78 Z1R and he took the speedo apart and recalibrated it himself for a sprocket change. It may be possible you could do that?