exhaust leak choke stove

Are you talking about the hot air valve between the intake and exhaust manifolds? If so, Remflex makes a gasket.

Nope i have the remflex gasket for that junction. This is the one i'm talking about...TFMbm6dQrWUbkam1yOhRwbdRU-6WIzCPFAly_6Yg-wQLQIUCRLph9n_iyj2CSObu8P2BQQ=w1753-h1314-no?authuser=0.jpg
a certain span of years in the middle of slant six production had this pocket open to the exhaust gasses the rest are sealed off