Use the Z590 for the steering servo. 85 oz/in isn't actually up to snuff for a steering servo for a savage but it's what you have. I would look for a better steering servo if it was me. Try to find something 170 oz/in or higher. The z270 would work ok for throttle and brake.
I'd use something like this
http://www2.towerhobbies.com/cgi-bin...p?&I=LXHZR9&P= 333oz/in @ 6V
Matt