400bird, the positive battery cable goes directly to the starter so tying your radio cable there would work OK. The only downside would be heat from the engine and exhaust, and dirt/water splashed up from the road. Heat is the enemy of current flow. Might be better to run a wire from the battery under the fender [above the inner fender] to try and keep it inconspicuous. Or perhaps forward to the rad support then down from there. The shorter the wire the better.