Headers on a 340 Cylinder 7

Hi I am having trouble with one header bolt on my 340. Its cylinder 7. I first tried a stock Transdapt hex but no way would it clear the actual header tube. So I ground down a significant portion of the header bolt flange and its still interfering with the cylinder (see picture). So my question to you guys who've "been there done that" what gives? What should I be using?

Thanks