100 horse shot of nos for 440?

Personally, if it were me, I would forget about the nitrous at this point. A 440 in that car, as a street driver will be a handfull just the way it is. If he/you havn't done it yet, upgrade the brakes and suspension. The 440 adds a fair amount of front weight. It will also have tons more torque, and will have traction problems. With nitrous it will most likely need mods to the wheel wells, to get a large enough tire on it. I have no idea of your sons driving ability. Let him get use to the car as it is. As a "street" car there is limited opertunity for nitrous use.