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I tried UBU to disabled the security check on the bios but the motherboard doesnt detect the modified “stock” bios from ASROCK. It will only detect the original bios for the board. I even tried to remove the security from the stock bios but it still doesnt detect it.
I also ran reports on both bios’s from UEFITool and compared the two. They both come back similiar the v1.5 bios(original) mostly matches the 1.2 bios from ASRock.
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Just an update more fiddling around. In case someone stumbles on this post with the same problem. This post helped greatly.
[Guide] How to flash a modded AMI UEFI BIOS
I had to use the Annex portion of the post. Essentially download the FlashTool Utilities.rar he has posted.
Follow his instructions on installation and backing up the BACKUP.ROM file. Then boot back into windows and grab a copy of the latest ASRock B450m a/c bios (as of writing it is 1.90).
I renamed this to MOD.ROM for ease of use. Dropped this file on the previously used USB.
Booted the USB and ran
flashrom -p internal -w MOD.ROM
wait for it to finish then reboot.
You should now have a ASROCK b450m a/c bios flashed 
ENJOY!
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