Yes, the crossover is a rectangle shape at the intake manifold edge of the heads (below that curved hollow at the center of the head) and intake, but changes shape as it passes through the head to the exhaust ports, and also changes shape as it passes through the intake manifold itself.

When the weighted and spring loaded flapper valve (heat riser valve) on one exhaust manifold (I believe its the right manifold, its been a few years) closes, it sends the exhaust back through the port on the head, under the pendulum on the intake, through the port on other head, and into the exhaust. If the flapper valve doesn't close, or isn't there, the exhaust heat drifts up (heat rises) to the intake. Over time (generally 8-10 years), the carbon from the exhaust plugs up the ports under the intake and at the intake manifold end of the heads. That carbon needs to be dug (chiseled) out of the ports.

As long as the ports are clean, there should be enough heat passing into the intake to help the cold running condition for several years. Gene