Wiring a 90's era Box/Tail lights to a 2006 Sierra

[MuskokaMike]

I can get any 2 working in any combination but can't seem to get all 3 (signals, running lights, brake lights) working at once.

Here's what i have so far.

Input harness to the connection block is 7 wires. I'm wiring directly to this harness, bypassing the connection block.

Black = ground
Brown = running lights
Blue = left or right turn (can't remember which blue is which)
Blue = left or right turn
Blue = Stop ( the blue opposite the blank spot)
Green = reverse
Brown/white stripe = running lights (I'm assuming the extra brown has something to do with the running lights staying on until you open and close the door)

Tail light harness from 90's era box has a 4 pin connecter and a separate ground wire.

Brown = running lights
Yellow = left turn
Dark green = right turn
light green = reverse

Black(separate) = ground

Where does the brake light (blue) wire hook to?

If I don't hook up the blue (brake wire) i have running lights, signal lights and the brake light on the cab works as it should

If I hook the brake wire(blue) to the brown, I have brake lights and signal lights but no running lights

If I splice the brake (blue) in with the brown to brown, I have signals, running lights but the brakes don't make the tail light brighter when applied and the brake light on the cab stays on with running lights.

If I pigtail the brake (blue) to both signal lights ( yellow and green), I have running lights and brake lights but when I activate left or right turn signal, both sides flash like 4ways,,lol

are they just not compatible? Is there no way to make everything work at once?