One solution I used many many years ago was: purchase 2 of the thin metal type gaskets and a thicker fibre gasket. Make a gasket sandwich along with some copper coat sealant. Torque it good and go for it. Hope you can find a solution cause leaky headers don't sound cool.
Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)
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