I think you'll get the idea. Cut that tail off, tap it for a male thread by 45° barbed hose adapter. Angle it forward and slightly down to get it out of the line of the pulleys and belts.
I thought about doing that myself but ran out of ambition. I thought of ditching the 2nd alternator but its not as easy as removing it. Its tied into a bunch of stuff not just extra charging capability.
If you added one do yourself a favir and keep it independent of the trucks wiring. Use it as you said for an external power source.
Mine was handy when the truck had electric plow, lights, and salt spreader. No flickering or issues but if you arent using it, its just another 500$ bill waiting to be replaced.