[Lynn Eades]

The end of each pipe has a sort of ball shape to it. This will allow the pipe to be poked into the cast elbow, and then moved to offer it up to the manifold.
There is no special seal of any sort. Its just a close fit.
Another aspect is that the motor will rock on the engine mounts (slightly)and the cast elbows are angled and sited so as to allow the pipes to move up and down as well as expand and contract, with heat. All clear as mud?
There is more to this. The floor will move slightly (relative to the exhaust pipes) as the carrier traverses rough terrain. With this all in mind, it make sense that the power unit is installed correctly with good engine mounts.