damn exhaust LEAKS!

i cant get these old rusted crappy POS Headman headers to stop leaking on my 318, iron heads...i tried new gaskets, new header bolts, plain copper gaskets...before i took them off, they didn't leak, and the gaskets looked like royal crap, i dunno how they sealed...now i buttoned everything up with new copper gaskets and they leak! WTF? should i try those mr gasket ultra seals instead? or maybe double the both of them up? what do i do?