• In addition to the upgraded Drive Gear (26391-06), there is also an upgraded entire Oil Pump (first installed on 07-later Sportsters). The new pump reuses the same kit part number as a previous version, making it difficult & confusing to know to which version someone is referring. The old (& new) part number for the kit is 26204-91A (which first showed up in model year 2000).
• The difference between the 2000 version and the 2007 version relates to the drive shaft, internal Gerotor return & feed gears and the body (which cannot be ordered separately). The internal parts for the new pump design are not backward compatible to the 2000 pump design.
• The only known external indicator to identify that the 2007 pump version is currently installed is the number 26213-07 which is stamped on the bottom of the new version.
• The upgraded pump is compatible for use on 1991-later Sportsters.

Here are the internal servicing part numbers from 2000 version and 2007 version: