This may help one other person on the Internet but if you have a CentOS guest OS and want to install Virtualbox Guest Additions you need the kernel headers. t yum install vzkernel-devel will get you the latest kernel headers.
enjoy.
I got a Mountain Cur and a ~~pitbull~~ big loveable cuddle puppy RIP Kimber 5/26/2022 RIP Yeager 1/3/2019 RIP TJ 3/25/2014 RIP Sugar Bear 8/29/2014 RIP Shilo 4/10/2015 RIP Yuki 2/19/2017