8.8 rear 28 or 31 spline axles

Not having the best of days today. I just finished putting my 8.8
rear out of my 00' Mustang GT Vert. back together. I ordered Superior
Gear axles which arrived at 31 splines. Removing my axles I find a
rather large differance in the dia. at the c-clip end. 28 vs. 31
spline. No help from Summit, Superior is on vacation until monday and
I have a 1,000 mile trip soposedly going on starting Thursday.

My question, after all the ranting bs I just laid on you is... Are
there 2 different live axle rears that were installed in 2000? The
new axles came in at 30-1/2" long according to Summit they are 30-5/8"
long. I could have miss measured. The old ones are 30-11/16" long, of
courese the same goes for these. Old ones are approximately 3/16"
longer than the new ones. Do I have a 98' and older 8.8 rear under my
Mustang possibly? Just looking for possibilities, thanks for looking.
Tag on rear info as follows... It is definately a posi rear.

(top line) S229G
(bottom line) 3L27 88 9L16


...Ron
--
68' Camaro RS
88' Firebird Formula
00' Mustang GT Vert