[jcassity]

these radios dont have enough amperage pull to even come close to blowing up any of the wires even in factory configs.
now if for some reason the voltage is stepped down,, well the current flow may be in question ,, i speculate 18-20ga on the interior is well inside the safety limits

wire needs one thing to be designed for the application and thats Watts.
P=I*E

insulation yes,, a factor especially when its location is near a known hot spot, yet i cant see you going wrong very easy with todays modern insulation designs.