Front end rebuild....buy new or rebuild?

You're both incorrect. The large ball joint started (in A-bodies) in 1973 regardless of which brakes you got. Also, early '73 still had 9" drum brakes as an option......usually standard equipment on a low line slant 6 2dr w/o A/C.
so '73 had 9" drums in front and the large UBJ? huh, learn something new every day...