I've checked my Tahoe taillight assembly few minutes ago.
What 'ive found is I have 3x 3157 bulbs which are 21w/7w but only 1 socket is 2 filaments ready : the tail/brake one.
All others sockets are 3156 wired.
The dual amber/white leds seems to work like a 3157 bulb :
1 ground wire
1 amber positive wire
1 white positive wire.
Best way to check if the are ok is to plug them into the tail/brake socket and turn on the light.
the bulb should lit up in one color.
they press the brake pedal and the bulb should change color.
Release the pedal and the bulb should go back to the first color.
I'll test them as soon As I get them.
My concerne are I don't want to modify the factory harness.
So I will create a "Y" harness that wil come from the 2 original sockets (turn and reverse) an joint into a female 3157 socket which will be fitted with the LED bulb.
I've found this on ee-bay :
3157 Socket
or
this one will do it too.
Here I found T25 (3157) empaty bases I needed :
autolumination.com
A pair of thoses wired to the 3157 socket and it'll be fine !