I recently bought a 66 corvair the crown conversion (327 in the back seat). I don't know much about the engine. It has the double hump heads and a solid lifter cam. I installed a atomic efi carb and a pro billet distributor with a 6A box. I had planned on just running race fuel mixed with 91 octane with no alcohol. I recently read that the lead in the race gas will screw up the O2 sensor. I would like to keep the engine in the car. If I run aluminum heads what are the chances i can get away with just 91 octane ? Thanks.