It's a duct in a box!
All the houses in our area from this era had central heat/air put in much later. How anyone lived around here without AC is beyond me. The downside of having retrofitted duct work is that it's super ugly and sticks down from the ceiling. We want the room to be nice looking so we decided to box in the ductwork in the room. Mr. Handy was particular about not losing any more ceiling height than necessary, so we didn't just have a box that was as wide as the widest part of the ductwork.
I was dreading this part of the project because there's a lot of measuring and lining stuff up to make sure that all your surfaces stay parallel to each other and square. It actually ended up not being so bad!
We also put in a pocket door frame that you can sort of see in the picture above, but we didn't take pics of that part. We are dry-walling the other side of that wall since we do plan to finish the entryway to the basement at some point in the future and to finish the basement bathroom as a full bath. With all the walls finally up on the inside of the room, it was time to start sanding and painting!