14.04 - How do I get identical kernel release and kernel versions across multiple systems?

How do I get identical kernel versions across multiple machines?

I have 8 machines which I want to be on identical OS versions. They originally started out as Ubuntu 14.04 installs (at differing times) and they've been patched regularly via apt-get update && apt-get upgrade && apt-get dist-pugrade. When I execute uname -a on these systems, I get several differing versions of the kernel release and kernel versions.

$> cexec uname -a 

************************* host-all *************************
--------- alpha-front---------
Linux alpha-front 3.13.0-132-generic #181-Ubuntu SMP Wed Sep 13 13:25:03 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
--------- alpha-back---------
Linux alpha-back 3.19.0-80-generic #88~14.04.1-Ubuntu SMP Fri Jan 13 14:54:07 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
--------- qa-front---------

Linux qa-front 3.19.0-80-generic #88~14.04.1-Ubuntu SMP Fri Jan 13 14:54:07 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
--------- qa-back---------
Linux qa-back 3.19.0-80-generic #88~14.04.1-Ubuntu SMP Fri Jan 13 14:54:07 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
--------- staging-front---------
Linux staging-front 3.16.0-77-generic #99~14.04.1-Ubuntu SMP Tue Jun 28 19:17:10 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
--------- staging-back---------
Linux staging-back 3.19.0-80-generic #88~14.04.1-Ubuntu SMP Fri Jan 13 14:54:07 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
--------- prod-front---------
Linux prod-front 4.4.0-31-generic #50~14.04.1-Ubuntu SMP Wed Jul 13 01:07:32 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
--------- prod-back---------

Linux prod-back 4.4.0-31-generic #50~14.04.1-Ubuntu SMP Wed Jul 13 01:07:32 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

The all appear to be on the same version of the OS

$> cexec cat /etc/lsb-release

************************* host-all *************************
--------- alpha-front---------
DISTRIB_ID=Ubuntu

DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- alpha-back---------
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- qa-front---------
DISTRIB_ID=Ubuntu

DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- qa-back---------
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- staging-front---------
DISTRIB_ID=Ubuntu

DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- staging-back---------
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- prod-front---------
DISTRIB_ID=Ubuntu

DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"
--------- prod-back---------
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"

So, kernel release 3.19.0-80-generic with kernel version #88~14.04.1-Ubuntu SMP Fri Jan 13 14:54:07 UTC 2017 seems to be the most recent. This is what I'd like to ensure all systems are running.

I've duplicated the /etc/apt/sources.list from my staging-back server to my alpha-front server and did the apt-get update && apt-get upgrade && apt-get dist-upgrade cycle and yet I still have kernel release 3.13.0-132-generic with kernel version #181-Ubuntu SMP Wed Sep 13 13:25:03 UTC 2017 (no apparent changes).

There are slight differences in the virtual hardware between systems (128MB RAM vs 64MB RAM, 16 cores vs 8 cores, 500GB root disk vs 2.3TB root disk).

What do I need to do to get identical kernel releases and kernel versions?

Any suggestions would be greatly appreciated.