For MaxPain, I happended to get the Lunsford Racing Titanium Turnbuckle 1 3/4 steering rod at my LHS. Yes it worked out perfect for me, but I also changed the servo arm to a Dynamite 1/2 Aluminum Servo Arm Blue DYN2560.
The Proline kit comes with a titanium turnbuckle, but no ball ends. I woud get the kit first and then decide if you needed a new turnbuckle and what size. Kit came with 2 1/4 which was long for me.
Here are some kit instructions:
http://prolineracing.com/howtotips/maxx-steering.html