What I have done in the past is used some brass tubing larger than the pushrod and teflon diameter. This gave me room to mount the pushrod seal on to. Then the pushrod is cut to size. I like to use a metal Clevis on the servo end and an adjustable threaded Clevis, plastic to avoid metal on metal on the steering arm. In some cases I use E Z connectors to allow quicker adjustments to allow the servo to be in the proper position.

A serach on Tower Hobbies using the words clevis and EZ connectors sometimes called screw lock connectors should give you tons of results.

Ryan