Take a photo of the steering column above the steering box say the first 12 inches include the rag joint. This is a clue on if it was a big block. Somebody could have changed the steering box shaft but this is often an overlooked item when doing a change over. With that photo we can tell from there expecially if a small block shaft. I can not quite tell from photo shine a light on it I think I see a bolt/nut about 3 inches up from the rag joint which is a good thing.