Broken mounting tab....

The internals of the 16:1 box will swap directly into the case for the 24:1 box.

The only thing I’m not 100% sure of is if a roller bearing manual box can have its bearings swapped into a manual box that originally had bushings. But my understanding is all of the A-body manual boxes were bushed anyway and only some of the B-body manual boxes had bearings.

Even if it was the case that the bushings and bearings have different OD’s it would be a simple job to have the case machined. But I don’t think that’s even an issue with an A body manual steering box case.

As far as welding goes, yes, you could have the case welded to put a corner back on it. Even if you didn’t have the piece it would not be terribly hard to make one. I will say that having welded on one of the aluminum manual steering cases before, it’s not super easy. The cast aluminum is quite porous, so, it absorbs oil and grease. So welding on an old cast aluminum case can be tricky because contamination is a pretty big issue with aluminum welding.