The red wire should go to a source that will supply power to the choke when the key is in the 'on' position only. The pink wire from the IGN switch at the base of the steering column is usually a good source, as it has a full 12 volts.
The pink wire will go to the + terminal on the HEI distributor. The brown tach wire is not a good source. Some people have even used the green wire to the TEMP sending unit. I like the big fat 12 gauge wire to the HEI, that sometimes looks orange because of age.