That D&B carburetor Jay has three photos of above is one that I rebuilt and sold at Chickasha a few years ago. Those carburetors are very common for a reason - they run great!
Does a D&B Harrington carburetor run better than a Holley NH? No, it runs about the same. I think that in the Model T days lots of carburetors might have been sold just because, as now, folks don’t try and fix what they have, because they don’t realize how easy it is.