Exhaust manifold leak issue ?

Had the 273 ( 65 factory 4bbl ) rebuilt and to my shame forgot ( too involved with new business ) to re-torque all the bolts.

Developed an exhaust leak at the forward right exhaust manifold. Tightened the bolts but still leaking so figured a burn thru of the gasket.

Not the case. Other than being carboned up and wet the gasket is "fine" as in no burn thru or evidence of any.

?....Should I try a double gasket "fix" or look to do something else ?

When everything disassembled I wire wheeled the manifold contact surfaces but no other aggresive surface prep'.

Ideas....? PLZ