Easiest way is to cut a small notch out of a piece of angle iron so it will be able to sit fluch agains the main part of the sprocket, then drill at least 2 holes to line up with the ones that are on the sprocket, bolt the angle onto the sprocket and place it so it either hits the ground or the sub frame, then pull on your ratchet like a mad man. I personally did it the easy way, since my timming sprocket just slipped and im re-building the engine anyways, I just turned the crank until the pistons rested against a valve, then kept pulling to break the bolt free. I do not recommend doing this.
head is off anyways, so the second option is not really an option.
...BTW your Bieber avatar is awesome.-Malone
Hopefully you have not affected the torque of the sprocket bolt...
I don't see the problem here. If the pan is off, just use a piece of wood between the counter weight and the block to lock the crank and keep it from turning. BTW, what kind of weenie impact were you using that would not remove the crank bolt?