273 harmonic balancer bolt

Hey everyone, I'm needing to replace my timing chain and already hit a road block. I can't seem to find a way to brace the crank so I can crack the harmonic balancer bolt loose. I've tried wedging a screwdriver between the flywheel teeth and bell housing but always slips out under force. Is the bolt reverse threaded? I don't have an impact wrench & the engine is still in the car. I've heard some brace the breaker bar against the inner fender and use the starter to break it free but the seems sketchy. What have you guys done when attempting this task?

Thanks FABO!!