Thanks. I think the tool I have should work based on the dimensions shown in the picture you linked to. There was also a note on the page where somebody said it worked on a CB750K2 which I think is the same engine I had when I bought the tool or very close to it. That was probably around 1980.

For holding the clutch in place, I also thought of using a strap wrench which I already have. I also though it might be possible to insert a block of wood in such a way as to sort of block the gear teeth and prevent it from turning but I'm not sure if that would work or not.