connecting exhaust to manifold

[barmanvarn]

Working on my dad's 1969 GMC C15 with an L6 (250?)......and excuse the perhaps dumb question......

I had to take the exhaust off to cut off the rotted out muffler and install a new one. I noticed the exhaust was very loose where it attached to the manifold. It hadn't been leaking and I didn't pay it much mind.

I've now put everything back together and do I have a leak at that point. What I'm wondering is it just that I didn't line it up well when reattaching or is there supposed to be a gasket of some sort?

The manifold end of the exhaust pipe has a rounded "ring" permanently attached about an inch from the end and that rounded ring seems to fit against/into a rounded indent in the circular manifold opening (hope I'm explaining that well).

So, am i needing some sort of gasket or is it just a dumb user installation issue?

thanks in advance