You can get a hinging plate off a "box" Impala, Caprice or Cutless. I have switch on my mustang, had a plate but did us it. It would work for you because the switch doesnt sit outside the body. I would have built mine out.
Referring to the Alternator, there is a another terminal that is direct feed to the Alternator to the Battery Terminal (bypasses the switch). It is for the the power to go some where after the power is shut off. If the power from the alternator has no place to go then it can damage the alt.
I think NHRA rules say that It needs to be visibly labeled as well. You might want to have another sticker added directly behind the plate. Instead of having to take off the whole reflector to see it.
I have mine through the right side of my plate for the street. Then at the track I remove the plate to see the stickers. Having it through the plate allows me to use it as a security device (not everyone would notice).
I have also put one through a tail light as well. Looks sweet, but regret chopping up a tail light.
Good Job, Safety First!