You could also think about using the aluminum gears from AndyMark
http://www.andymark.biz/am-0143.html
http://www.andymark.biz/am-0521.html
And the spacers
http://store.andymark.biz/am-0156.html
This would save about 0.85 pounds per transmission according to AndyMark.
I have never used these products, but I have heard that they are the same great quality as everything else AndyMark.