header gasket blow outs

[al's71gmc]

Iv'e put about 7000 miles on my truck since purchasing it and keep having it blow header gaskets. When I got it, it was blown on the driver side, back 2 ex. ports. I replaced them and about 4000 miles later it was blown again. Now it is starting to make noise again. Anyone else have these problems? Is there a better gasket available? I don't know what brand header is on my 350, but the po thought they were hookers. Iv'e had cheap thin headers on another rig do this, but in that instance the flange was warped. When I bought new headers it solved the problem. These flanges are about 3/8" thick. Any ideas? Thanks, Al