But the factory LS1 crank reluctor is a good 9-10 inches in dia. and meant to fit on the back of the crank in the crank case. The sensor is 3 or so inches long to reach it through the block. I would think putting that behind your harmonic balancer would be a pain in the butt.
What did you have to do to the last dizzy to make it fit the engine? How much room is behind your timing cover? Does behind harmonic balancer mean outside or inside timing cover?