I finally got this figured out, thank you all for the links and help in this stupid problem lol. I would love if there was a "grub only" iso that you could install, but sadly there is not.
SOLUTION:
- Install Windows onto HDD1, unplug HDD1, install windows HDD2.
- Plug in HDD1
- Make a 10GB partition on any of the drives
- Install Ubuntu to that partition
- Make sure Grub is installed and working (you can boot back and forth between windows installs)
- Boot from live linux USB (choose "try ubuntu")
- Mount the partition that has the full ubuntu installation on it.
- Using thunar, delete everything, EXCEPT - /boot and /etc/grub*
- Use gparted to shrink the ubuntu partition to 100MB
- Use gparted to extend the windows installed partition
- Sadly, windows won't automatically see this partition change, so I ran chkdsk on it and that fixed the incorrect partition sizes being reported. I think there is another way to refresh that tho.
We now have GRUB as my bootloader showing both versions of windows allowing me to pick between each either at a full power off (shut down) or after a hibernate. I am finally happy lol.
NOTE: Grub makes it's own partition to hold the UEFI boot stuff in it. This partition is what shows up in the BIOS boot menu of your device.
PS: You can take a backup of the drive and if ever need to redo the process, you can simply make a 100MB partition and copy the backup back, then use the live usb to reinstall GRUB.
EDIT: have not tested, but diskpart > rescan drives should update the partitions without doing a full ckdsk