From Kurt's Z10 report...
"There were a limited number of RS/SS coupes built via the option code Z10 that received the pace car style orange Z28 striping, essentially coupe versions of the pace car. Paperwork documenting why the cars were made has not been found, but they were sold in the Southwest area of TX, OK, NM, LA, and AZ (though one documented car was sold new in TN). The option was somehow communicated to dealers in these states (probably via zone letter) and the dealers then placed their orders (Chevrolet did not build cars without a dealer or customer order)."
Paul