i'll take that bet, Q. i dont really want to give you hell, but i s'pose i must. at least we got the puns out of the way.

the 2.56 is a 1-series, and the 3.23 is a 2-series. i'd have to say you can only go up to a 2.78 from a 2.56.

the 2.56 and 2.78 use one bolt pattern
2.93, 3.08, 2.93 use a second pattern
and the 3.36, 3.55, 3.90, and 4.33 use a third.

at least according to-
axle ratios, tempest and firebird
i cross referenced some part numbers using that site, and it is consistant within the book. this is also basically the same as what salmon38 quoted earlier, just from a different book.

of course, there's nothing like real world experience to prove a book right or wrong....

and if you have a corporate c-clip rear, such as out of a camaro or nova, the splits are different.