Several months ago, I did a major coverage, with pictures, of flywheels and bell housings and another on starters. The one about starters was SPECIFICALLY about factory, GM Delco type starters. Any aftermarket/mini starters may present a completely different situation.
You can probably find both by doing a search, or maybe someone will throw up a link.
But, for now, here is the answer to your specific question, as I understand the question.
14in DIAMETER, 168 TEETH FLYWHEEL/FLEXPLATE:
You need a starter nose that has the STAGGERED bolt pattern (remember, this is for stock GM Delco type starters).
There ar TWO versions of the staggered bolt pattern starter---alum nose and CAST IRON nose.
When using a manual tranny (such as a Muncie), 168 teeth flywheel and 621 style bell housing, you MUST use a starter with the cast iron nose.
A starter with a cast iron nose will work with EITHER an auto tranny/168 teeth flexplate. But a starter with the alum nose will ONLY work with an auto tranny/168 teeth flexplate.
So, to get a starter with the correct cast iron, staggered bolt pattern, ask for a starter for something such as a 68-72 Chevelle with a BB and 4sp.
Then, when the parts guy hands you the box with the starter in it, open the box to confirm that it has the iron nose.
Why is the end of an iron starter nose smaller than an alum nose? I have ZERO clue! That's just how they made them.
Most of the rebuilt starters that I've seen for GM engines which are sold by reputable parts stores (NAPA, O'Reillys, etc) are GOOD, dependable starters. I just checked at my local O'Reilly store a couple of weeks ago on a BB/4sp starter-------------the parts guy brought out the right one with the iron nose-----------------my cost, $40!!!
By the way, while we're on the subject, I have never seen a straight across bolt pattern starter nose that was cast iron--------------they were all alum.