Here are three different square port, 4-2-1 exhaust manifolds. Two are about the same.
This is casting number N22. This seems to be a common one I've run across in wrecking yards and is the most common in 510s sold in the States.
Here is a detail of the ridges along the middle two runners. These normally sit beneath the heat shield that the foil hose off of the stock aircleaner connects to. You can figure how the hot air is vented into the hot air riser for cold weather conditions, and the ridges probably serve to help direct hot airunder driving conditions, where there would be turbulence under the hood.
This is casting number A35. I yanked this one off of a L18/A87 pickup. Notice there are no ridges cast onto the center two runners. Also, the collector is turned outwards a tad more than the N22.
This unit is casting number U60 in full configuration. Not too sure what this came from, but it is very similar to the N22, except that you can see a pipe threading tapped into the rear of the collector for recirculation of exhaust gasses into the intake. Also, there is additional casting on the front mounting tab.
