Audio Systems: 2000 E-150 Ford Van 6-CD AM&FM Changer, ford vans, ford wiring

Question
Ernesto,
I pulled the Radio/CD player from the dash of the E-150 Ford Van and compared the factory speaker wires to the Ford Wiring chart and they match up. I then went to the back of the Van looking for a wiring harness going to the back. I found one on the drivers side and I opened it up ripping some electrical tape back but the wires I need are not back there. I then followed the wiring up front where it goes along the roof line on the drivers side and open the harness up there and still could not find the color coded wires that I need for the rear speakers that come from the plug behind the radio. What do you suggest I do from here? Should I just use 4 blue snap locks and connect new rear speakers wires for the back speakers directly to the wires I need a few inches behind the radio in the harness coming off of the radio/CD or is there somewhere else I should be looking to connect the new speaker wiring. The harness coming out from behind the radio goes in to a fat harness near the firewall and branches out to the left and right under the dash of the 2000 Ford E-150 Van. I wish I had a schematic of the wiring so I would know where to look for these 4 rear speaker wires I need to attach to.
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The text above is a follow-up to ...

-----Question-----
Dear Ernesto,
I most recently purchased a used 2000 E-150 Ford Van that has a Ford 6CD Am&FM Changer in the dash. The radio and changer work great. My question to you is that the Van only has 2 speakers one right and one left in both front doors. I would like to add two more speakers to the rear doors of this 2000 Ford Van just like the rear two speakers that are factory installed in a 2003 E-350 Van that I also own. I need to find out where to wire these other 2 Ford Speakers that I picked up for the back of the 2000 E-150 Van.  Is there a factory radio wiring chart showing a color code for say 2000-2003 E Series Ford Vans that I can make a copy of? I would like to wire these 2 extra speakers right to the back of the Factory Am&FM CD Changer or wherever else this needs to be done. Thanks ahead of time for any help you may be able to give me here.
-----Answer-----
you nned to follow the last plug on the cahrt and the speaker wires are plug in to the back of the radio you just need to find the wires in the back of the van
http://www.installdr.com/Harnesses/Ford-Wiring.pdf  

Answer
the cables are back there they are just hard to find or sometimes they go to the back and then they make a u turn and go back  so they can be in the midle of the vehicle  i seen them go on the roof or the floor of the  driver side
yes the other option is just to run all 4 speaker wires