Leaking exhaust flange

Don't see where we're talking about the stove pipe -- looks like we're talking about the headpipe-to-manifold-outlet flange, to me. There's no stovepipe on a slant-6 that has a gasket junction with the exhaust. '70-up engines got a sheetmetal stove around the central collector of the exhaust manifold and a flexible duct (sometimes called the stovepipe) running from the stove to the thermostatic air cleaner snorkel. The '70-'72 slant-6 exhaust manifolds do have an open stove rather than a cast-in pocket for mounting the automatic choke thermostat. These '70-'72 setups have a stainless steel cup sitting in the open stove, gasketed to the exhaust manifold and clamped by the hold-down bolts of the choke thermostat.