Every 1969 Camaro was built to a specific dealer order. The order could be for dealer stock or for a customer; the process was the same. Hence there really is no 'special' order.
Unless otherwise specified a Z/28 was built with a 3.73:1 non-positraction rear axle. If positraction was specified the car would be built with a 3.73:1 positration rear axle. However the Power Team Chart shows that a Z/28 could be ordered with 3.07, 3.31, 3.55 or 4.10 axle ratios. 410 or higher required posi. There was at least one 69 ordered with 488s.
Your car was ordered with that axle, probably for a specific customer that never took delivery. I hope it has a wide-ratio trans.