Need help adding radio to 65 mustang

I am adding a second radio in the trunk of my 1965 ford mustang (keeping the original in dash radio, well original). As many of you know, new radios come with blue (power ant), red (ignition), black (ground), and yellow (memory) wires. I am a novice electrical guy...very uninformed, but ambitious...a planner before jumping in. Since the radio and amplifier are both in the trunk, I plan to connect the radio yellow, blue, and black wires to the amplifier +12V, REM, and Ground screws, respectively. How do I find the ignition wire under the dash to run it back to the radio for the radio red wire? Please help and correct any of my plans. Also, when it comes to speaker wires, the one with the stripe in it. Is that negative or positive?

My radio went into the dash (without modification to the dash metal) and looks oem. My graphic equalizer went in the glove box. The amp and CD changer both went into the trunk.

For the radio and graphic equalizer, I used a tap at the fuse box for pwr source. It's a brass fitting (think upside down question mark without the dot) which fits between the end of a fuse and the fuse contacts in the fuse block. The straight end sticks out and a female blade type connector slides onto it. Available ad a lot of auto parts stores.

The amp gets it's power from a dedicated line which runs from the battery + terminal, through the firewall, inside the frame rail, through the right rear fender to the amp. This was using an amp connector kit, available at Radio Shack.

When the radio is turned on it turnes on the graphic equalizer, which sends a signal via the blue wire to turn on the amp.

As for which wire is positive or negative, that depends. Different manufacturers use different means. If the wire came with the speakers, it "may" have two different size blades; the wire may be marked with plus or negative signs along it's length; one wire may be copper and the other silver; etc. while it is important to have the correct positive lead, it's even more important that both leads be the same; both leads to positive having the line or not, and both leads to negative having the opposite.