Ignition Switch Connector Fail

7 would be a strange gauge here in the states, "commonly." typical gauges you'll find in these cars is 18 would be about smallest, and 16 / 14 / 12 / 10

Some of the larger platforms like C bodies might use no. 8, and battery cables were OEM no. 4 for the most part.

This is always specified in OEM diagrams such as the factory service manuals, which you can download there from MyMopar.com