I have a complete new HD shaft with bronze gear but don't know the part number but i can measure it if you wish. It's been listed in this for sale section.
Stock type pump uses the stock length pump shaft, Milidon system with one of their pumps without the spacer may need the middle length, check your set up to make sure The Milidon system using the external pickup between the pump and the block use the long one Make sure the pump drive gear is seated on the bushing by installing it before you install the pump and due what you want to do to measure it your way