Thanks Mike. The number of bolt holes was the biggest thing that I was questioning and still am really. I've been reading everything anything I can find about it. I think three is correct for some, but not others. Not that it helps much... From what I saw they moved to three bolts because of cracking nose cones. I can't really confirm it though.
I also saw some guys talking about the cast code on the starter nose cones being date codes, but I don't think it is. Mine says 730 which by their rationale was the 73rd day of 1970, but I've seen pictures of too many 1st gens with similar numbers ending in zero.
It looks like the common number to identify these parts is 10MT. Does that sound right?