Stay with what you have the 850 will be fine.Being this is a street car, you will have better throttle response and drivability. The 950 might show a bit more top end power at the track, but will be doggy on the street. with a 31" tall tire and 4.56 gears you should go through the top end at 6500 rpm i had that combo in my camaro.
How much converter do you have? at least a 4500 stall.
