Just out of curiosity, you're not trying to use the black "reinforced" gears in your M03 are you????? If you are, those are touch bigger than the "white" gears and need a little trim to make them work. Frankly, not worth the effort. IMO not any better than the stock ones.

If the stock gears are used, it is impossible to build a rough gear box in a M03. Yes, the parts need to be in good shape, but that's a given.