Intermittent Ignition Issue [66 Valiant /6]

Battery (after two 30 min drive and sitting for a half hour) measured 12.9v. On startup fell to 12.6v before stabilizing again at 12.5 on idle. Attached pics show battery connections, current starter relay, old one, and the other new one that also worked (yellow). Need a pic of the ignition? Car has an aftermarket temp gauge that comes on with either accessory position, a speedometer that plugs into the cigarette lighter and an aftermarket tach.

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