Don’t use a resistor to drop voltage just wasting power. Use a regulator. 6Ahr battery would discharge in about 30 hrs without even being used by just having that resistor in the circuit.
That's only if the circuit is closed.
There is no resistance in an open circuit.
It's as simple as installing the resistor beyond the main switch, like right next to the starter's solenoid.
BTW, I installed a battery disconnect switch to the solenoid.
There's also anti-theft feature, so the starter and ignition can't be hot-wired.
There are many components offering resistance in a car's electrical system.
However, all of them are controlled by various switches, disconnecting them from power.
Using an ohm meter, if you were to search for electrical resistance at the battery, you'd find nothing.
If you did, it would eventually drain the battery.