Chris ,why do you shift at 5200 ? If you have a diesel stroker crank the guys at nissan motorsport told me you can turn to 7000 rpm with no problems. If you are already turnin low 13s you ought to run mid 12s easy. Double check with your master tech that built the motor that thing has just got to be able to stand 7000 rpm. I am assuming you have forged pistons,but with even cast pistons 6400rpm should be resonable!!!