I soldered on the remaining four Optocouplers needed for the other sound FX triggers on the Adafruit board. It was kind of tricky getting the soldering iron into such a tight space but I managed to get them all in along with the Resistors. I had to use a lot of jumper wires to make my necessary connections (left) so it looks a little crowded but it works.
I also soldered in four more 3mm screw terminal blocks for the Switch Pod & any other special button I want to use to activate these particular sound effects. These are not like the ones connected to the other screw terminal blocks & Optocouplers as these do not need a DTMF tone request, either because the Switch Pods already have one built in or it is not desired for how I will make use of the sound effect.
I have also made changes to my "Pin Outs" diagram to reflect the new changes (right). As you can see in the video I posted above the module is working fine and doing just what I want it to do. All I need is those few missing components for the 12V to 5V conversion for the Adafruit board but that is a minor detail, once I get those parts and solder them in I can do a test with the module temporarily wired up to a few buttons in the car. Next will be to place the whole thing inside of a project enclosure to make it look a little more attractive, not that anyone is ever going to see it lol ;)