Fox made a B case .40 as well as the C case (Compact) .40. AFAIK the B case .40 never came ringed, but the .45 is ringed. I remember reading the .40 B case came in ferrous lapped construction and ABC, but I’ve never seen an ABC version. The flat flange mounted carb is a B case and the square bore necked carb came on the compact .40s. IIRC the B .40 was about 1,000rpm faster than the compact .40 on the same prop.