There are three different spindles. The long spindle (don't have one here to measure) fits all Commandos from '69-'74, except MkIIA. These had a short spindle. Both of these used the single 1/4-18 bolt in the middle to anchor the spindle to the cradle. The MkIIA was shorter because it used the thick felt behind the end cap plugs and was "permanently" lubricated, much like the MkIII spindle. The end caps were welch plugs swaged into the end of the cradle and did not have a zerk fitting or long thin bolt that held the earlier end caps.
The MkIII is the same length as the MkIIA, with the exception that it has two flats machined in the middle to take the two cotters that anchor that spindle to the MkIII engine cradle.
You can use a MkIIA spindle in an early cradle by using the MkIII bushes and oil soaked felts in the center of the spindle and each end. Use the end caps for a MkIII.
I don't know that all MkIIA's had this short spindle set-up, I picked up a short spindle several years ago and puzzled as to what it fit, did some research and found a part number listed as a MkIIA spindle. So if any of you have a MkIIA with the long spindle, I'm not saying it didn't come from the factory that way, only that there exists a short spindle with a part number description that it is for a MkIIA.