Obviously it wasn't clear enough....! So here some pics and ... pls take a look at that chart again! This is a SAE #2 to SAE#3 adapter ring. Bolt circles are 18 3/8" and 16 7/8" respectively and holes are equidistant. Same for a SAE#1 but bolt circle is 20 7/8".
A little boring, I know, but...
Like I said before: Only the 5ton MF bell housings are #2. That ring out of a 7.3 Navistar perfectly fits on that LDS465-1A housing! But all of those 13 studs of the deuce MF are on a BC of 18 7/8" which is completely odd!
And by looking at your pic, your CAT isn't a #2 either!? BC might be 18 3/8" but the bolts/studs are not equidistant.... And BTW, you said you milled the back side of the adapter flat??? How did you do to exactly center it to the bell?
Hope this ......!