Looking for correct bulbs for 1965 Plymouth Valiant 200 for Instrument Cluster

Depends on the LED.

Some have resisters that burn off the excess wattage. Others use electronics to switch the voltage on and off in a duty cycle.

Some are dimmable some are not.

The 158s in most cases have lasted 50+ years but LEDs while better now might not (regardless of their claims) how much do you like taking your cluster out?