[AndrewL]

I'm glad you posted this. I just dug my old Harlan shift light out of storage and would like to install it for old times sake and was wondering where people were getting their tach signal from.
For positive power, if you want to keep tapping into other wires to a minimum, you can buy an add a circuit that will let you piggyback off an existing fuse so you can draw power via an existing circuit for power

For the other stuff, I'll defer to the guys who've actually done this on their Z.