Change from Manual to power 67 Dart

The power steering box needs to come off of 67-72 A body, the the 70 box will work fine.

The 73-76 PS box had a larger shaft coming out of the bottom so the earlier Pitman arm won't work on the newer box.

The other 67 difference that you're referring to is that the IDLER arm on the 67 K frame is mounted differently than the 68-72 Idler arm.
This will not affect your conversion.
The 67 idler arm and drag link on your car stay where they are.

You will also have to switch out the steering column and coupler. The shaft is longer on a manual steering and the coupler has different diameter splines. The 70 Dart column will NOT work because it has a key in it and the 67 column does not.

Good Luck!