Stroelman - Your measurements do seem to be at odds with the Tech Tip info. I suppose it's possible that your starter has had previous repairs/rebuilds and may be made up of a conglomeration of parts and pieces. Guessing that your previous experience with the starter, when it did work, did not include grinding or frequent missed starter drive to ring gear engagement??? If that's accurate then it's at least correct for your existing flywheel.
To possibly learn more on what your current starter is, I would suggest a thorough cleaning and search for the stamped part number and date code on the case exterior. Then post that info here and we can try and help confirm what the starter is, which can lead to helping you find rebuild parts (they are still out there as noted in Bill Hanlon's post above) or a suitable replacement.
As Bill mentions above, doing the rebuild yourself is a good possibility. At the same time, have you searched for a local starter rebuild shop? Some can still be found, although that is becoming harder and harder these days.
