Need help replacing plastic spur gear with metal

[holly nitro]

So I have the parts I need but, it seems to be alittle to thick, the thread lock on the nut does not go all the way down on the transmission screw there are two slipper pads then the spacer is this normal

 

[alpinehyperlite]

Out of curiosity, why are you going to metal?

 

[holly nitro]

I keep stripping the plastic and chewing up slipper pads this has two pads its better