A common issue with header gaskets blowing out, and/or sealing poorly, flange bolts loosening etc., led me to do some research on this subject..I was happy that I did.
I used Percy's Splitlock bolts, and Rem-flex gaskets on my BBK headers, and have never had an issue.
Rem-flex gaskets are designed to allow for some headers that are not 100% true, (which leads to the leaking/blow out issues).Just follow the directions re bolt torques. You don't need to squish the heck out of them for a good seal.
The Percy Splitlock's are easy to install, and definitely will not back out if installed as per the instructions..