Using the kit dimensions for the turnbuckle lengths seems to be a good place to start.
Step 1: Build the steering bridge. A light dab of blue threadlocker on these ball ends is suggested.

Step 2: Attach to the aluminum steering arms. A very LIGHT dab of blue threadlocker is suggested; don’t get any on the shims or bearings.

Step 3: Build the 3 turnbuckles; two steering, one drag link.

Step 4: Attach the turnbuckles to the steering assembly.

Step 5: Slide the steering assembly onto the steering posts and secure with the 3x6mm screws. Blue threadlock is suggested.

That was quick and easy. Moving on to Step 5 – Suspension!