The tach would hook up to the coil wire to get the rpm reading, then the normal power, ground, and accessory wires. The power you can get from any source that gets power when you move your keys to the acc position. You wouldn't want constant power. The ground, I think that's self explanitory. The accessory, you can hook that up to any light's wire, like an interior dash light that comes on when you turn on your head lights. The A/F gauge, the power and ground are the same as above, and the purple wire goes to the O2 sensor. I don't know how many wires the 02 sensor of a Z32 has, but the instruction manual should tell you which to use if the Z32 has a multiple wire O2 sensor. I haven't messed with a voltmeter, but I'm sure someone else here has, or if not maybe on the 70-83 forum. Good luck and have fun!
82ZXT