anyone wired in a retrofit radio for a 67-69 Barracuda?

Restoring a 67 cuda and decided to go with a retro fit radio and was wondering if I could get some advice. Having trouble on what wires I should use
Here's what I am doing. Way cheaper than one of those retro look radios. I made it so you can input your AM factory radio into it and it will play through your rear speakers. You could also just mount this box under your package tray, run 12 volts to it, connect your speakers and play your music from your phone via Bluetooth. Check out the thread below.

The Golden Age Of Wireless