My opinion of "peak" torque is the figure is useless! This is a thou shalt not exceed value that will guarantee letting the magic smoke out! Use continuous torque ratings as your design value. You get the needed torque to do your design by speed reduction of the servo to the shaft by means of timing belts or other recognized means. Remember, the torque value specified for steppers is the "holding" torque at 0 rpm. It drops off after that and you need a spec sheet to know what it will do at the rpm that you need.
In an attempt to ans. your question about those servos, I would say a qualified YES. What is the max rpm you want the lead screw to rotate. Then take 3000 x .8 (Mariss recommends pushing to no more than 80% of max rpm) = 2400 and divide that by the desired max rpm and this will give your reduction factor. There are many variables to consider here such as the pitch of your lead screw, the load you will be required to move etc. This is why I say qualified. Then you can multiply the 90 oz-in by this reduction to see what your effective power will be at the lead screw!