Well
To answer your question the steering servo needs more than 150oz in torque and speed depends on the driver. I like faster servos at .10-.14 transit time, but a bit slower shouldn't hurt, but torque is the most important in a steering servo and remember that endpoints arent the only thing that can cause problems in a steering servo, the servo saver needs a bit of room on the spring to relieve the servo during a crash, Locking down the spring is just asking for trouble.
The throttle servo needs at least 100oz of torque to stop the car well, and I do feel speed is important in a throttle servo around .14-.10 transit time. I find the throttle servo can be less than the steering servo, but in my car I use Ace DS1313 servos for steering so if something happens to it it's only 80 bucks to replace, and I've had good luck with those servos in buggy, but in the throttle I like the Futaba bls451. It's brushless and is really smooth and fast and the gears on those new futaba servos are so nice and being in the throttle that futaba won't get torn up being in the throttle, just make sure you don't make the servo push the brakes harder than the brakes can go, if you adjust the brakes properly you won't need to cram the servo too hard anyway.
Now keep in mind there are other good servos, those two brands are my favorite though....