Take all the engines you've noted and determine which one is almost 2 pounds lighter than any of the others but still has almost the largest displacement. Also which one is the only 6 port engine in the group? Nobody else can figure out how to do more than 4. Now allow that two of them have a block mounted carb instead of a rear mounted carb, making for a stronger case. Only one of them has a one piece crankcase with a cover at each end. Not having a split case is once again stronger, and lighter.

BME 115 wins easily.