What is this part?
Could be a bracket for a belt drive for some accessory, water pump or generator? The slot could be to tighten the belt.
I think Mike's on the right track. The portion of the gizmo in the upper right of the photo looks like it replaces the water outlet. If that's so, then it's not difficult to imagine its orientation in the engine. Of course, it could replace the water inlet.....
I would say for a chain driven starter generator Delco made one for the T that mounted on the drivers side and it was up high, That part is usually missing from the generator set up.