Well,
I am putting my car together and putting in my USA-66 radio. I noticed that on the original radio, there are only two wires, while this radio has 4, in addition to the 8 speaker wires.
The wires of concern are the Red/Main Power(ignition), Black (ground), Orange/Memory Back-up (battery), and Yellow (auto antenna). Which one of these wires connect to the black wire and the black wire with blue stripe currently in the car. Where do the other two wires go to?
Thanks in advance!

 

Assuming you have a Mustang, you also neglected to include your model and year, I'm not sure how to hook up the radio. Ford does not vary wire colors that much, my 99 van has many of the same colors as my 65 Fastback, but switched power to the radio comes from a black/red stripe wire.
Jim

 

You have either a 65/66 fastback if memory serves correct. One of the wires is a switched hot lead that should connect to your red wire from your radio. Use a test light or multi-meter with the key in the acc position and test each lead. After you find the switched 12V± lead, verify it by turning the key to off and you should have 0 volts. Connect your black lead from the radio to the radio support bracket or another nearby ground. You'll have to splice your orange battery wire into a constant hot wire. I believe the lighter is always hot (verify) which you can easily tap into without cutting using a crimp-on tap.