Send GIGABYTE an e-mail. They once sent a GA-970A-D3 owner a VRM heatsink for free (i.e. the same one put in the rev 1.4 D3) (the post is somewhere in the 990XA/970A owners club) and I'm sure they'd be glad to send you one for your purposes. I hope I'm not too late.
In the meantime, you should avoid installing the N520, or you may get reliability issues. The latest F9 BIOS or later has VRM protection equipped; with your VRMs not cooled, you may see reliability compromises in the form of VRM protection activating as a result of the VRMs not getting the cooling they require. This may cause you to lose saved work among other things.