Also, what are you trying to gain by putting LEDs into the brake lights? The reflector is designed to properly fill the lens and yield properly distributed output from a filament bulb. The geometry of drop-in LEDs is so different that they tend to result in erratic light distribution. They may look brighter from some angles while being significantly dimmer from others.
LEDs may reach full brightness faster than filaments, but any safety benefits will be negated by the improper light distribution making them much harder to see from some angles.
If you're looking for brighter brake lights, I'd recommend replacing the stock 3157 bulbs with 3457. They retain the same filament placement (and therefore lens fill) as the stock bulbs while increasing the major filament from 32 to 40 lumens.