Where to get power for aftermarket tach?
I got my light power supply from the tail lamp fuse. The green wire to positive side of the coil.
Uh,,,,,,,,,,,,,,,,I hope you meant the negative side of the coil
Lamp power could probably just as well come from the same place all other dash lamps come from --the output of the headlight switch, cluster dimmer control, which feeds the "INST" fuse. Find an orange wire, like the radio connector
IF you have MSD or some other aftermarket ignition, refer to the manufacturer's destructions for the trigger wire. Some systems need a "tach adapter."