Originally Posted by Citoriplus
They would only need a resistor if they worked as turn signals and only if they were not wired in series with the bulb or didn't have an electronic flasher unit driving them.
If they are just being used as marker lights they are probably wired in parallel with the normal tail light bulb so they would still go on even if the bulb died for some reason.
I can confirm the need for a resistor on the rear turn signals. I swapped the rear to an LED and now it blinks twice as fast. I just haven't taken the time to wire it yet.