Flaming river rack and pinion?
Doesn't sound like a std rack set up.Should be tie rods(threaded shaft) with tie rod ends.....no coupler.
1) center rack
2) thread on tie rod ends.( there should be flat spots or a hex near the threaded end of the tie rods to put a wrench on.
Do you have heims/ rod ends with a coupler OR tie rod ends?
Either way.....if rack is centered, the tie rod/tie rod ends should be close to equal length in a preliminary alignment.