I had a '66 Buick and the exhaust manifold had the inverted bevel hole for the exhaust pipe just like the early 216s. It did not use a donut there. The exhaust pipe had a ball end formed onto it which fit into the beveled hole in the manifold. It had a flange similar to the 235 flange used to force the ball into place. As it was tightened, the ball end of the pipe form-fitted into the bevel. A good muffler shop should be able to form that ball end on your exhaust pipe.
