Thank you for your reply.
I apologize for the rough sketches, but the shafts seems to be identical, except for the splines (and the prop nut attachment).
Further research would seem to indicate that the switch to a 23-spline was 1958 for Johnson…I can buy a 23-spline dog, but will it properly engage the ’57 gears? Am I falling down a rabbit hole that I ought not go down?
