For a nitro touring car?
I am assuming yes, so I will say I have a Futaba S9402 as my steering servo. It is perfect, if anything, too much.
.10 sec @ 6v
110 oz of torque (or something like that)
As a minimum, I would probably say .13 sec/60 oz for throttle and .13sec/70oz for steering. Others will differ in what they say, but my main piece of advice is do not cheap out on your servos! Cheap stuff performs cheaply. I won't name brands, but you should know what is cheap, and what is not.