Tachometer wiring

In this model, Those "extra" male spade terminals are there only because of the way the buss bar was formed. They would cut the bar material to any length and have minimum of 1 connection point. Anyway... Those unused terminals are not on the fused/line out side. You can pick up switched 12 volt there but a inline fuse is still req'd. A much later model might have a unused terminal on the fused/line out side at orange or yellow wire circuits.
You could get the illumination with a T-tap wherever the orange wire is handy/accessible. Radio, ashtray, etc...