Best starter DIY ever, courtesy of Vyndictive:
DIY: Starter Change Swap (for dummies)
"your starter will have the part number "N3H1"... if you have "N3H1 A", that means you have an upgraded starter. The other product number for the upgraded starter is "N3Z1" which came from later model years.... The non-upgraded starters are also about an inch shorter than the upgraded ones."