Battery is 100% good

Sometimes I'll get a little click when I turn ignition but it doesnt last long

Not getting power to lights or radio etc.

Is this: ignition switch?

Starter?

I can't figure it out

Could be loose or corroded battery connections or cable ends. Not likely starter or solenoid related (other than connections) if you're losing power to headlights.

When you check the battery voltage, it sits somewhere over 13 volts, in the vehicle, connected?

So if the battery is good, then it can pretty much only be cables/cable ends not making good contact.

Lights are wired direct to the switch, they don't go through the ignition switch. They may be powered through the fusible link on the starter solenoid, been too long since I looked at that.

What changed since the last time it worked correctly?
Joe