7 1/4 to 8 3/4
I almost forgot that I had to have a custom driveshaft made because the 8 3/4s third member stuck out farther than the 7 1/4s. You might be able to find an original driveshaft out of a 8 3/4 car with your same transmission, but i couldn't so I just had Dennys Driveshafts make me one.