If you are currently running a 10si then we must assume the brackets to mount it have already been fabricated. Just replace the alternator with the same part # that you now have and you are on your way. You have had your current alternator tested, right?
BTW: your truck is not “completely stock” since it didn’t come stock with an alternator. It had a generator from the factory. Therefore, it’s “mostly stock”, just being nit picky.
