I assume you attached both the original and patch ROM image.
I never deal with the 270X, so, please only take my comment as "for info" only.
The Mac EFI should start from address 10000, however, your patch ROM's Mac EFI start at F800, doesn't looks right to me. Also, apart from some basic info (e.g. It will ident you card as 7950, the ROM version is 113-E2080B-624, etc), the whole real EFI part only contain zero but nothing else.
A normal Mac EFI should end at 1FFFF, but your patch rom end at 1F7FF. Then the old unpatched content (looks like from the original UEFI GOP) start to show up again start from 1F800.
TBH, the whole Mac EFI part looks very wrong to me.
HOWEVER, if the unpatched one is the original ROM, then the UEFI part is actually start from F800. So, the patch tool may actually correct to start the Mac EFI from F800 in your case. But I still don't think this is a correctly patch ROM because the Mac EFI part basically only contain zero.
You better post your whole process with screen captures. So that we can see if there is any error.