I have an 8" fabtech lift with the torsion bars turned up. I want to lower the bars down to original position. How do i know where it should be sitting at

I dont have an Immediate answer but if noone else chimes in I would check the Install instructions to see how much they were cranked when installed. Then possibly you could get a judgment from that.

The ideal "height" of the front suspension is with the axles level or slightly up hill to the hubs. That way when you are on the throttle and the front end lifts, the axles will be strait.