Need correct Pitman arm
Manual steering boxes for all A, B and E bodies have the same size sector and splines, they're all the same for '62-76 A-bodies, 62-72 B-bodies, and 70-74 E-bodies. So, just buy the right manual pitman for your centerlink.
Only C-bodies and vans had large sector manual boxes. Power steering boxes were small sector 67-72 and large sector 73+, not manual.
All the info is in that Big block dart article
Steering Box Info