I just went through this myself so hopefully I can help.
I would recommend starting closest to the switches and working back to the back of the truck. For the brake lights, do you have power coming off the brake lights switch (down by your brake pedal) when you depress the pedal? If yes, the brake light problem is further back, if no, then your switch is bad.
The brakes lights go through the turn signal so your problems are most likely related. Since you've replaced the turn signal switch and seem to be having problems with which wire go where, I've "liberated" this from an article on another site. If Keith is no OK with that, he can edit my post, I have no problem with that:
There are 7 wires to the turn signal switch, here is a description of each:
* Blue/yellow stripe: horn.
* Blue: +12V power from turn flasher for turn signals
* Black/red stripe: +12V power from stop lamp switch for stop lamps
* Green: Rear right turn/stop lamp
* White/Blue stripe: Front right turn lamp
* Yellow/black stripe: Rear left turn/stop lamp
* Green/white stripe: Front left turn lamp
Here's how it works:
* When the turn signal is off, both rear stop/turn lamps are connected to the stop lamp switch. To test with multimeter, check for continuity between the red/black wire and the yellow/black and the red/black and the green wire. Lack of continuity indicates a bad switch. To check with a test light, clip the ground wire onto one. Put the probe end into the yellow//black wire slot of the connector (either side.) Press down on the brake, if the light illuminates that side works. Next do the green wire the same way.
* When you turn left, the connection on the left rear is broken with the stop lamp, and it is connected to the turn flasher, along with the front left turn lamp. Turn the lever to indicate a left turn. Now check for continuity between the blue wire and the yellow/black wire and the blue wire and green/white wire. Lack of continuity indicates a bad switch. There should still be continuity between the red/black and the green wire. To test with a test light, turn on the turn signals (and turn the key on so they work) and indicate a left turn. When you insert the probe into the yellow/black wire slot of the connector or green/white wire slot the test light should flash. Put it in the green wire slot and press the stop pedal, it should light.
* When you turn right, the connection on the right rear is broken with the stop lamp, and it is connected to the turn flasher, along with the front right turn lamp. Turn the lever to indicate a right turn. Now check for continuity between the blue wire and the white/blue wire and the blue wire and green wire. Lack of continuity indicates a bad switch. There should still be continuity between the red/black and the yellow/black wire. To test with a test light, turn on the turn signals (and turn the key on so they work) and indicate a right turn. When you insert the probe into the white/blue wire slot of the connector or green wire slot the test light should flash. Put it in the yellow/black wire slot and press the stop pedal, it should light.
If you are using a swith from a different year truck, there may be color changes in wires, but this should help alot.
Finally, you can test the power coming out from under the dash in a more handy location under the hood. There is a connector there that has the 4 wires that head to the back of the truck. If you disconnect it, you can test the 4 wires while standing up.
Hopefully that will get you started, please feel free to ask more if I didn't help out or wasn't clear.
