Download Oracle's VirtualBox 5.2 from here:
Create a new VM called macOS and configure your settings like so:
Once setup is complete, exit VirtualBox and open a Command Prompt with Administrator Privileges. Now copy and paste the following commands into your Command Prompt.
cd "C:\Program Files\Oracle\VirtualBox\" VBoxManage modifyvm "macOS" --cpuidset 00000001 000106e5 00100800 0098e3fd bfebfbff VBoxManage setextradata "macOS" "VBoxInternal/Devices/efi/0/Config/DmiSystemProduct" "MacPro5,1” VBoxManage setextradata "macOS" "VBoxInternal/Devices/efi/0/Config/DmiSystemVersion" "1.0" VBoxManage setextradata "macOS" "VBoxInternal/Devices/efi/0/Config/DmiBoardProduct" "Iloveapple" VBoxManage setextradata "macOS" "VBoxInternal/Devices/smc/0/Config/DeviceKey" "ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc" VBoxManage setextradata "macOS" "VBoxInternal/Devices/smc/0/Config/GetKeyFromRealSMC" 1 VBoxManage setextradata "macOS" VBoxInternal2/EfiGopMode 5 VBoxManage setextradata "macOS" VBoxInternal2/EfiGraphicsResolution 1280x1024 VBoxManage setextradata "macOS" "VBoxInternal/Devices/efi/0/LUN#0/Config/PermanentSave" 1
Now close the Command Prompt and reopen VirtualBox.
You need to do these steps the first time you start the VM, once configured it will save the changes permanently. The only time you need to run through setting up EFI, is after doing an update.
Start the macOS VM and immediately begin pressing F2 to enter the UEFI Boot Maintenance Manager. Once you enter you will see the following screen:
Highlight Boot Maintenance Manager and press enter. Then select Boot Options and press enter.
Next select Add Boot Option and press enter.
Select the EFI entry and press enter.
Select EFI again and press enter.
Select Clover and press enter.
And finally Select CloverX64.efi.
Highlight the name field and press enter. Input the name of Clover for the Boot Entry and press return. Then arrow down to Commit Changes and Exit and press enter.
Select Change Boot Order and press enter.
Select Change the Order and then highlight Clover.
Move Clover by pressing the + sign to the top of the list.
Now Press F10 to save changes to the boot order.
Arrow to Return to Main Page and press enter. Then arrow down to Reset System and press enter to restart. You should be greeted with the main Clover Bootloader screen. Press enter to Boot the default entry into macOS.
From within the VM download Clover Configurator, once its downloaded launch it.
Once you've generated a new serial number restart so clover will load with it. Then try logging into iCloud.
Download SierraAMD installer from here and add it as a secondary drive to your VM:
cd /Volumes/SierraAMD/PostInstall sh post.sh
Once it's done, exit and reboot. You can now remove the 10.12.6Installer.vmdk from your list of drives and return to just having macOS as the only entry in Clover.
Gigabyte Z370 HD3P
GTX 750 TI 2GB RAM OC
32GB of RAM
High Sierra 10.13.6
Windows 10 Pro X64