Well, this reminds me of a mistake I made with one of these gearcases.  First, be so careful that the part you received is not “mismarked”.  Sellers oftentimes mark out the original part number on the box, and make the assumption it is OK to just mark the superceded part number on the box.  In this case, I don’t think the part number of the clutch dog has changed/superceded, but there is surely a chance that the clutch dog was mismarked in error.

Years ago, I was trying to help out a friend with his 40hp gearcase.  I thought it would be a great idea to “update” the clutch dog and prop shaft to the spring/ball type used on later models.  Needless to say, none of the part numbers for his engine superceded to the later model part numbers.   I got the gearcase all together, sealed up, pressure tested before trying to shift the gears.  Could not get it out of neutral into either forward or reverse.  What the heck  could be wrong….  Pulled it all apart only to see that the diameter of the “updated” clutch dog lugs was greater than the original clutch dog, so it wouldn’t fit into the forward/reverse gear cavities.  I ended up having to locate newer style gears as well in order to make my “great idea” work.

In your case, it doesn’t “look like” that change would affect anything, but who knows.  My advice is don’t make the mistake I did….  Assemble the gearcase “dry” with no oring/sealer to ensure that clutch dog will work properly before going through all the work of getting the gearcase sealed up properly.  Only to have to rip it apart again.