If you can swallow the price, Stage 8 makes the best header bolts you'll find. They have a keeper and e-ring that fastens on to each bolt to keep them from vibrating loose. They're expensive at $50 for the set, but they look good (chrome) and work even better. I haven't had to tighten a header since installed them 2 years ago on my daily driver.
If you always do what you've always done,
You'll always get what you've always got
If you always do what you've always done,
You'll always get what you've always got