My old '74 Sportster is and XLCH. Some where along the line an electric starter was added. How canI tell if it's a Prestolite or Hitachi? Besides a Harley logo it has "P664a" stamped on it.

 

Prestolites are longer and skinnier than Hitachi starters Also the terminal that one attaches the positive from the battery is located further in toward the left side of the bike The Hitachi has this terminal at the end cover (further toward the right side of the bike ) Look at a catalog with pics you will see

 

This is the Hitachi starter.



This is the Prestolite starter.
The end caps (on the right in the views above) are different and this may be the easy way to tell which you have.............pg