65 dart no start

If the headlights don't come alive that is a HUGE clue.

FIRST THING I'D DO and this means REGARDLESS of how you perceived their condition, is to CLEAN the battery posts and clamps.

If that does not work, then determine

1...if the battery has any power under load
2...if the power is being lost in a clamp/ cable/ end terminal.

You need at absolute minimum, a 12V test lamp and better a multimeter

Be methodical. AFTER cleaning the clamps, and IF THEN it won't work,

A ... Turn on headlight switch, and if they will not light, put your meter/ test lamp probes on the two battery post CLAMPS. You should get a bright light/ about 12V.

B...If not, stab your probes directly into the posts of the battery. You should get a bright light/ about 12V

If so, RE clean the posts and try again

C...Repeat above. If you are showing power at the two CLAMPS with the HL turned on, and no headlights, now

Connect one test lamp or multimeter probe to the engine block/ ground. Recheck at the POS post clamp. If you have power, move + probe to the big stud on the starter relay. If you have power there and no headlights, time to get the shop manual/ diagrams, as it is likely in the firewall connector/ ammeter/ other wiring.

FIRST FIX THE HEADLIGHTS. If it will not crank then we'll go from there