Would an ignition coil cause no power?

I have a 1979 Ford ranchero 302.
No start no crank no radio but I have headlights no dim when I turn the key.
New battery, relay and starter is good.
Trying to determine if it's the ignition coil or ignition switch.
It has started right up a few times but mostly nothing when turning the key.

Test the coil? Is it spitting out sparks if you hold the high tension lead close to the engine block? If the thing isn't cranking when your turning the key the coil is most likely not the problem Id be looking at the ignition switch
hot wire it? Wire from battery positive to coil positive take the other positive wires off the coil if your going to do that then screwdriver the starter motor does it start?

Did you check the ignition fuse

No, it will cause no spark but everything else will be normal. Your problem is likely the ignition switch.

Are you positive the relay is good? Have you checked all connections and grounds? Did you jump the relay?

"It has started right up a few times but mostly nothing when turning the key."

not "likely* starter circuit and coil circuit (including ign switch function/path for both) are both intermitantly acting up (not definitive).
sounds to me like simple starter circuit cables are marginal. Check all connections. Neg and positive.

pos cable from battery through relay on inner fender, then down to the starter itself. Check little wire going to starter when down there. Key in start position, that should read 12V minimum.
neg cable from batt to front core support. Plus at least one engine to chassis/fire wall ground strap.
check under cable insulation for signs of white powder. Indicates time to change those.
"starter is good"
did you remove it and have it bench/load tested? That check the solenoid at the starter as well. Starters, once removed, can be tested at most auto parts stores for free.

do note, this starter system is stand alone. It is not dependent on any other circuit.

Neutral Safety switch?

Seriously check all connections. Undo the battery cable at the starter and clean everything and put it back together. That can cause intermittent problems.

Sounds more like a bad ignition switch or starter circuit wiring issues… Not likely a coil issue… Since the radio has no power either. A coil issue would not affect the radio. Check for blown fuses too.

The starter relay has a couple yellow wires on one terminal… One of which powers the ignition switch circuit for the starter. In that wiring is a fusible link wire which may be bad too.

Fusible link wire looks like regular wire but internally, it is 4 gauge sizes smaller to act as a slow blow fuse and protect the circuit wiring from frying due to a short or overload. So if the circuit uses 14 gauge wire, the fusible link wire will be 18 gauge.

I'd test the yellow wire that runs from the starter relay to the ignition switch to check for good power. If you get power at the relay but not at the ignition switch, then the fusible link wire may be blown. Look for signs of melting or arcing on the wire sheathing near the relay. Parts stores sell fusible link wire in various gauge sizes.cut out the old one which is likely spliced into the yellow wire at the relay terminal and take it along to match up for same size and length. Usually, there are markings on the sheathing of the fusible link wire which gives a gauge size or ohm rating of resistance value. Then splice the new fusible link wire in place of the old one with new terminals/connectors… Check the circuit for any shorts to ground… Frayed wiring, corroded connections, etc.

If you do get power at the ignition switch yellow wire, then check for power at the red/light blue stripe wire at the switch which carries power to the neutral safety switch and then onto the starter relay to operate the starter. A white wire spliced into the red/light blue also powers the ignition module.

Could also be a bad or misaligned neutral safety switch. You can jumper a small piece of wire or paperclip across the two terminals at the neutral safety switch wiring harness to bypass it for testing… If it starts with the jumper wire installed, then the NS switch is bad.

Wiring diagrams…