Your car shut off? How do you accomplish something as involved as a nitrous installation with the car running?
If the car won't turn over it certainly sounds electrical in nature. Unless the engine is seized (yours isn't) the started should always at least be able to turn the motor over-- regardless of whether it runs or not.
EDIT- your stupid assed threads are really starting to piss me off. You are impossible to help, because its never clear what your story is. Initially, it sounded like you already owned a stroked 5.1L 2V engine in a Bullitt Mustang. Then you fess up that you really only have a kit on order. Then I read this thread where it sounds like you took your 'I was driving it yesterday' Mustang and blew it up on a nitrous install while the car was running. Now I see a thread on Page 2 where, no, in reality you have already blown up the car and the block is not only out-- it has already been bored 0.030 over (which is too much on a 4.6 block).
Why is it so hard to simply tell the truth on here? We can't help you otherwise.