Backup & Restore Question

I'm looking at backing up My 10 Year Old Ubuntu Server ( AMD System )for the purpose of turning it into a VM on my KVM Virtual Machine Server ( Intel System ). In my case I have My operating system with servers & software on 1 HDD and My second HDD / LVM LV data drive that gets mounted when the OS boots. I have the same setup duplicated on KVM with a NIC Card passed through. I've moved all data from one LVM LV to the other I'm just down to the OS Drive. I Was thinking of creating an image of my OS drive, converting it to .qcow2 Image and mounting it, I figure I'll probably need to 1. rebuild grub, 2. Change the /etc/fstab file to match the test OS in it's place to make sure I could mount the .qcow drive inside the LVM drive.

Is there a better or easier way?
Is there anything else I may run into?
Would I be better off using .tar and just replace the filesystem? then I'm not sure all my servers will start up If I do that. I don't have any experience with this, would like to know the best way. Any help would be greatly appreciated...