Header help

[olred68]

I bought a pair of flow tech headers and put on my truck last week after I had the exhuast put on I have a bad leak around both headers. I am running the copper gaskets I made sure I didnt have anylose bolts someone told me to remove the headers put a straight edge on them and take a belt sander and flaten to make them all the same if ones higher than another.I just want to know what you guys think would be the best fix. Thanks Brandon