If the lights are just dimming at idle, that is kinda par for the course with Dodges.
BUt improvements can be made.
Be sure to remove and clean battery terminals. If you see white or green corrosion, replace the cables.
Be sure to recharge that battery fully on a grid powered charger. You cannot rely on the alternator to fully recharge a dead battery, despite the masses believing so. Perhaps a several hundred mile drive would get a dead, jumpstarted battery back to near full. Around town driving, never. Ever. .
Remove and clean battery to engine, battery to firewall and frame to engine ground. If no Frame to engine ground exists, add one. The alternator is probably grounded to engine block or head somewhere too. Remove and clean this.
Voltage drop in the headlamp circuit is a huge issue. Headlight output is not linear with voltage, but exponential. The stock headlamp circuit goes through the bulkhead connector, through the headlight switch, through the dimmer switch, back out to through the bulkhead connector, then off to the headlamps. All this wiring is undersized, all these connections get crusty and induce even more voltage drop. The result is that the battery might be at 14 volts, and the headlights are seeing only 10.5v.
If you seek brighter headlamps, a new harness with relays triggered by the stock wiring is not difficult to do and will shorten the circuit length considerable and feed the headlamps the voltage they desire.
A headlamp getting 14v will be twice as bright as a headlamp getting only 10.5 volts. if the battery is not fully charged then the dimming and brightening with more rpm will be more pronounced.
Good luck.