I agree on the horsepower being in the 700 range with current setup,given a decent chassis. First off, you say peak power is 9,000 and you shift at 8700? Peak torque is 7200 and stall is 7,000?
My deal makes peak power at 6900, and shift at 7450 and 2/3 at 7300, stall is 6200, but peak torque is 5,000! I dynoed the motor and it said 847 hp, car weighs 3065, i use 2078 Goodyear slicks that weigh 41 lbs each, and the car went 8.900 at 2100 da.
The point of all this info is if ypur tq and hp peaks are what you say, the stall and shift points may be a big part of the problem. Too low. Its dyno time! Get the real dope on the motor and go from there.