Copper exhaust gaskets

I'm using the Mr Gasket copper gaskets on my 273 with vintage Blackjack headers. Always had trouble with the old style gaskets blowing out between cylinders 3-5 & 4-6. No leaks or sounds of any kind in the 4yrs they've been on.

I used a set of the aluminum composite gaskets on a 350 70 GMC pick up with Flowtech headers & had the same great results.