The Shaker 500 does not have RCA leads on the back. The SWC+ and SWC- contacts won't really do you any good, as RCA-style connectors require both pos and neg for both the left and right channels.
There are a couple of options here. One slightly dirty way to wire it would be to buy a speaker-level to line-level convertor which could be spliced into the speaker wires going to the rear speakers. This convertor, sold at any car audio store, would allow you to get signal to the amp, but the signal would have more noise (distortion, not volume), and thus your subwoofer wouldn't be as clean. You'd also lose some volume on your rear stock speakers, but as you would be running an amplified sub, you may not notice. You can run the remote amp on/off wire off of any switched power lead in the car. The backside of the radio has one. Consult the wiring diagram you have for which pin this is, and simply splice into (not re-route) it.
The second option is one that I am not sure you can do, but I have heard that the connections for the Shaker 1000 trunk-mounted subwoofer are actually in cars with the Shaker 500. I don't know this for sure, but if they are, I'd bet that you'll find all the power, remote on/off, and signal wires you'll need right there. If the harness is not in the car, I'd bet your local Ford dealership's part dept could sell you the stock Shaker 1000 radio-to-sub wiring harness. Cleaner install, but I'd bet much more labor intensive.