If I have an exhaust leak at the manifold to head interface, I take the manifold off and get it planed (surfaced) to get it flat again. Then I use a steel composition gasket to help insulate the manifold from the intense heat that likely causes it to warp in the first place. I think Chrysler was just too cheap to not put them in place the first time around.
Generally, I hate taking exhaust manifolds off of B engines though, at least in some years. I have found they had cheap studs in the head to hold the manifolds in place at least in 1969 and 1970. In 1971, they seemed to have improved the grade of the stud so they don't break with just very little torque applied to loosen the manifold nuts. If you break one of those studs, you pretty much have to take off the head and have the remainder of the stud removed and high grade studs put in or live with the exhaust leak. I have cursed the cheap engineers that made that choice many times.