If you are 180 off on the timing, the engine will only backfire when you attempt to start it. If its running, then its not 180 off. Isn't the Harmonic Balancer keyed so as to make installing it wrong impossible? Are you sure your timing light is being triggered on the correct cylinder? Does the light have a timing adjustment knob on it which may be "adjusted".
2008 manual GT with deluxe trim, Edelbrock e-force, FRPP GTB Mufflers. 3.73 gears, Coast Ultralight Drive-shaft. 18" OEM Polished Bullitts, Webelectric Sequentials, XM built into the Shaker 500. Alarm and Escort RedLine.