Generator Drive Gear

I am going to use a 12 volt generator,similar to a 29975-65A(late sportster) with a 4 spline keyed shaft on my 45 lower,does it really matter what drive gear I use ? Thanks I could use any help.

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I am going to use the big generator screws and was thinking about using a 14 toothed gear out of a sportster ,maybe a (oem#31073-63).