belvedere rear end

well, its finally time to change out the rear end on my dart. started out a 72 dart, slant six, 904 and 71/4 rear end. now has a 5.2 magnum, 904 and same 71/4. i'm going to use an 8 3/4 from a 67 belvedere. i'm still using the original 6 cyl. drive shaft, and i know i'll have to shorten it, but wondering if the small shaft would have the same u-joint as the 8 3/4? i hav'nt been under the dart yet to measure, but the 8 3/4 yoke is 2 1/8 inside. i believe that's the 7260 am i right? thanks, dave.