Potential ignition issues

If the battery is OK, put it on a slow charger. It's always best to begin tests and even start a car with a fully charged battery.

In the mean time you can use it with a voltmeter (or test light) to help track down the problem.

Here's a diagram of a '63 which I beleive is similar to a '64. If there are things that are different, post 'em and I'll correct.
Concept is the same.

Power source is either the battery (wires labled A) or the alternator (wire R6).
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Ignition switch gets power from J1 (red 12 gage wire). On the switch the terminal is marked B for Battery.
Headlight switch gets power from L1 for headlights, and pink wire from the hot side of the fuse box powers parking lights.

From the "ignition switch",
J2 powers the ignition when running, Q2 powers everything else that is switched on.
J3 and S2 power the ignition and the starter relay when starting.

So with the engine off, testing the unswitched circuits such as parking lights is a way to determine if power is flowing to the mainsplice from the battery.
if not, look for a break or damage at the connections between the battery and the main splice.
If it is, then turn the key to run or accessory and see if power is making it to the heater fan or turn signals.