About modding the 980DT heat sink, please take a look of the picture below (corner was cut out already). You can compare with yours and see the changes.
If you align the MSI 1070 with the 980DT heat sink, you will find those power phases popping the copper panel and preventing the GPU core from making good contact with the heat sink. Especially the individual one in the corner. I used a hacksaw to cut out the corner, and used the 400 sandpaper to deep-sand the places that I circled, following with refined sanding using 800-grit paper and 2000 grit for polishing. This required a lot of works, I would say adding extra (maybe 3) heat pipes on top of the 980M heat sink would be much easier if you don't want the trouble.
About the vbios of the 1070, I will recommend to wait for what @prema might come up later or a modded nvflash. Because at this moment, as I know, any modification of the pascal vbios cannot bypass the nvflash and requires a programmer to program it. This involves extra spending in a programmer and higher risk of bricking a card easily.
I can't provide the vbios because it's not my property. I found it in a chinese forum; if you search "vBIOS硬刷 Pascal GTX1060/70/80" in google, maybe you will find the original thread.
The below post by Dreamonic is a reference of editing the pascal vbios using hex-editor, I tried to mod it by myself and resulted in black screen on boot, not sure what is the cause.
http://www.techinferno.com/haven/threads/94/