Eric, I found this on a thread over at ifsja, thought it might interest you.
"the 12 bolt was used in the rear of 1/2 ton stuff till around 1980,when it was replaced with the 10 bolt.
it is comparable to a 44 in every way-shaft size and splines,ring gear(little bigger,i bielive),pinion shaft size,housing,etc. there is absolutely nothing that would make a 44 any better,assuming the same locker and gears in each axle.
the only difference is C clip axles. rear discs are easy,so convert it to discs and run it.
my friend runs a 12 bolt in a cj7 with 36" buckshots,a 360 and a t18 tranny. he beats the snot out of his rig and the 12 bolt has been there about 4 years now with no issues."
Good luck, Dave