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did you use it on both sides of the gaskets, or instead of the gaskets?


Yes on both sides of the gasket.

I don't think you could get it to build up enough to be used as a gasket, and if you could, it would only work the one time since the head and headers are two different materials that expand/cool at differently

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed