Depending on what steering gear box you have, there may not be another pitman arm to use. The sector shaft in the steering gear dictates the pitman arm, then the the idler arm must be the correct companion . In that case you would need the correct center link.
The simplest indicator is the hex nut holding the pitman arm on. If ia 1& 1/8 socket fits it its pre 73 power or manual. If you need a 1&5/16 socket for that nut its 73 up power steering gear box. I'm not exactly sure on the 73 year model changes either.
I wont get involved in the head banging going on in this thread. I will say some mix matched combinations of these parts simply cannot be put together no way no how.
Other combinations can be put together wrong but don't look or work exactly right.
Your parts may not hit once the car is on the ground until there is enough movement in the idler arm at K member bushing.
I can only suggest you figure out what combination a previous owner has came up with before seeking parts like a pitman arm that does not exist.
Good luck