63 Dart Mystery Circuit Board Washer

^^ That would be correct^^ Here are how dimmer controlled dash lamps work:

The park/ tail light circuit must be working. The headlight switch must be in "park or "head" and the dimmer control twisted some to the left. This results in power going through the dash dimmer control and out on the TAN wire where it goes down to the INST fuse. From the INST fuse, dash lamp power is branched off on orange wires

So BOTH the tail and the INST fuses must be good for the dash lamps to operate.