I've ran every size converter you are talking about(12.11.10,9,and 8 inch) on the street and at the track, the older B&M O69J nine inch worked really well on the street and at the track until it broke The last T/A 8 inch SS converter I put in my old Duster is still being used at the track and on the street by the new owner It was easier to drive and .2 ET quicker and 2.0 MPH faster in the 1/8 mile than the ten inch custom built street and strip converter I had built for that car off of the dyno sheets for the motor Buy the best converter you can get, do NOT compromise All the good eight race converters I know of multiply torque more at the hit of the throttle, not so much on the larger size converters