1966 dart power steering info

If the box you have is from a 73, then it will be the large (1 1/4”) sector shaft box and I don’t believe anyone makes a pitman arm to fit the 63-66 a-bodys for that shaft. You need a 72 and older box with the 1 1/8” shaft to have the correct pitman arm. Dead giveaway is the pitman arm ball joint should be facing threads up, in 73 they will be facing down. The one you have won’t work