Electrical problems 73 duster

Is this automatic column shift? If so you likely got the neutral start switch linkage out of adjustment. Try holding the key to "start" and wiggle the shifter from park through neutral and back.

Also if you do not have a shop manual, run over to MyMopar.com and download it, free. Some of those manuals got there because of some of the guys right here

Did you hook the ammeter wires up tightly and is there any suspicion that terminals in the various connectors are corroded loose?

Dash cluster grounding is also a probably issue. It is wise to install a ground pigtail on the cluster and bolt that to the column support or dash frame