Correct rear axle for 1970 Camaro L78

[JHS]

I am trying to confirm what rear axle ratios could be ordered with the 70 L78. I have been told that one had two gear options and both had to be posi units: a 3.55 (COX code) which was std. and a 4.10. The only 4.10 units I can find in Colvin's book are COO and CRE codes and neither being posi units. Would a COO unit be correct for my car and should it be a posi unit?