the neutral safety switch not working wont cause this problem, but i would fix it if possible so as to not be accidently starting the car in gear...... the wheels should turn when its jacked up regardless of locked up or not, but if it doesn't stall then it is possible that the converter is locked..... also check your fluid level and make sure its right.......should check it while engine is running car in neutral... if you dont know your cam specs then its hard to tell what speed converter you need, but if its a stock to mild cam you can get away with a stock converter, if its a little more lopey of a cam, you might want to step up a little more on the stall speed