What Shift Rpm

The first time the car was together everything was the same except factory magnum heads, 12lbs boost and 275/60/15 mt drag radials. My wheel spin was terrible. 2.0 60 ft 11.46 time 122 mph. So I am gonna try larger tires with the same 3.91. No dyno on the new setup but with the 12 lbs and stock heads it made right at 670 hp