Servos size is standard and won't be a prob. It will fit.

Look at the spec on the servo, usually what you see quoted is servo torque at 2 voltages, 4.8 and 6v and a servo transit time. The torque is obvious, bigger numbers mean a stronger servo, transit time - smaller number means a servo that reacts faster to your input. Price generally increases as torque increases and transit time gets smaller.