If you go with a small spline steering box that is 1972 and down you will need the 68-72 and down centerlink, 68-72 pitman, 68-72 idler. The tie rods will need re-adjustment but will work for both setups.
While you are at it, check the K-member to see if it is a 73-76 spool motor mount type vs the 68-72 biscuit motor mount type. Was your car originally a /6 but now a V-8?
Do you have large bolt pattern rims front and rear?