Stock exhaust leaking

[cuda67]

Does anyone have any suggestions for stopping exhaust leaks? I finished installing the 360 magnum in the 67 a week ago friday. I am still tying things up, wiring, tuning, etc. I am also trying to stop exhaust leaks at the joint for the exhaust pipe and manifold and I am having no luck. This is a stock exhaust and I have tightened, adjusted angle of exhaust pipe and it still leaks. The joint is like a flared fitting joint, the exhaust pipe is flared and the exhaust manifold fits into the flair, no donut. Is there anything I can check for or am I missing something? This exhaust came off the 318 I pulled out and it did not have donuts on it either, is that right?

Thanks for any suggestions.