http://users.bigpond.net.au/blitz_trucks/MODELS.html
"TOWING EYES…Chevrolets C8, C8A, C8AX and C15 all have their front towing eyes mounted to the front bumper so that they swivel in a horizontal plane. All other CMPs have them mounted so that they swivel in the vertical plane."
This is from observation, mine and many others!
Regards
Rod