You don't need to read Japanese.  Simply look at the diagrams.  The 250 and 360 columns to the right of the part numbers clearly show which model takes which part and how many are needed... like 6 screws or 1 pressure plate.  A blank in the 250 or 360 column means that model doesn't use that part.

If you want to read the text, use the Google translate app with your phone camera.  It will translate on the screen as you point camera at text.  Pretty cool.

But if you just want to screw around and replace parts and try random ideas and hope you get it to work, that's fine too. 

I've found the early parts diagrams with the columns for each model to be far more accurate than the screwed up online ones but even the best Yamaha literature is not always perfect.

Adding steels is probably not much different than using the correct spacer.