As long as you do a compression and leakdown test, and the motor comes back as ok, you'll be fine. Might want to get an MSD window switch to shut off the nitrous just before the auto tranny shifts. Since the nitrous is flowing at WOT, you are always at WOT in an auto, even while shifting. It won't negatively affect your motor at all, unless you misuse it. Mounting the bottle in the trunk is your best bet.