Quoted from NextoPin:
can I mix LED flashers with incandescent flashers?
Yes. I have them mixed on my F-14.
Depending on where you add them, you might not need to remove warming resistors as having incandescent flashers in the same line will prevent the LED flasher from being lit all the time.
Otherwise you have to remove the 330 ohm warming resistor at the flasher board where the specific flasher is connected to.