On a car with an old style relay controlling the flash rate, replacing any bulb with an LED will increase the flash rate. This is due to the complete indicating circuit needing to see a certain resistance. It's the same situation as if one of the bulbs was to blow. The relay and timing circuit would flash faster due to the decreased load.
I had bought LEDs for the indicators but never fitted them (i did the other tail lights, rear lights, fog and brake lights, including the high-level brake light, and the front side lights)
Guess what - when i tried the LED on one of the indicators that side would blink fast - sorry about that
I know you had a go at me about checking your maths, but I did say, any change to the loading of the flashing relay will increase the flash rate, or at worst not cause the indicators to flash at all.