I am putting in 2 HP500 EFI's in my boat and figure I will replace the couplers while the engines are out, here is the weird part. The engines had 2 different couplers on them. On has a long nose and one basically has a flat nose. Looking at Mercruiserparts.com there appear to be 3 different Bravo couplers available for this engine. A long nose one. An aluminum standard one, and a steel standard one. And a Design 1, 2, and 3????? So which ones should I buy? Apparently they will all fit since mine had one long and one short, but what is the best one to use? Why?