I think I read somewhere that the Bravo is an inch or 2 deeper in the water than the Alpha so something to consider if you're using the existing transom cutout and just drilling the 2 extra holes. Depending on how your's is currently set up you may need to go to a shorty to maintain the same prop depth as you have now with the Alpha.
couple months old but you people are mistaken. alpha and bravo are the same length input to output shafts. it is the TRS that is 1.7 inches longer. they went same size and cutout (for basically every drive manufacturer) so every boat manufacturer could hire minimum wage idiots who can only understand 1 set of instructions.