Tachometer...

I dont think you can because looking at this diagram it looks like connector A pin 4 for the tach models have an rpm signal wire there. BUT the no tach model has the same connector A but there is no wire at pin 4. there is a hole for the wire but the wire is not there... if u get what im saying

 

A diagram will show only relevent wires, unused ones are often just not mentioned.

I have seen threads on here where people swapped out instrument clusters to get a factory tach, that leads me to believe the connectors are wired for both.

It may be a week or two before I can check the connector, I'll report back then.