Keep in mind you'll need a wire that has +12 on it at all times in modern radios so it doesn't "forget" settings. You'll still need the switched +12V too. Unlike the factory units, 'most any car radio made in the last 35 years or so has "floating" speaker outputs, ie-don't ground them or you'll damage the receiver.
. Right that's why I'm trying to figure out what would be a good constant wire to use from the dash harness. I figured I'd use the red from the original radio power source for the acc power but kinda lost on the continuous power source atm