Power to Manual Steering Clarifications Needed
All of the A/B/E body manual boxes use the same sector shaft diameter (except C bodies and vans). They did not change in ‘73, that was only the power steering box. The pre-73 power steering boxes used the same sector shaft diameter as the manual boxes, they’re the “small sector” boxes. A small sector power steering pitman arm fits a manual box just fine, the year of the manual box doesn’t matter.
More info here
Steering Box Info