If it's the late '67 style box with the rag joint then you are not going to be able to use it. The collapsible setup has a 1 1/8" sector shaft which is where the pitman arm attaches, the earlier '67 box with the long shaft and no rag joint has a 1" sector shaft which is the same as a 65/66 setup.
I don't think you can use the pitman arm for either '67 setup in a 65/6 steering assembly because it has a different mounting system to the centerlink... and the idler arms are different too. Perhaps you can swap the whole late '67 setup in, this I do not know.
Your 65 box uses a 1" sector shaft so you want to stay with that so your pitman arm and linkage all stays the same. I assume from your post that you want a short input shaft box so you can use the collapsible pieces from the later models?
Ford actually used a box in some 67 Mustangs that had a short input and a 1" sector shaft. These would be a SMB-C for manual steering (19:1) and a SMB-E for power (16:1). These would be fairly hard to find because Ford only installed them during a short period of time in the 67 model year. If you can't find one of those, you should be able to get a rebuilder to rebuild the spare 67 box and change it over to a 1" sector shaft so it would more easily fit your car. It would require changing the sector shaft itself and the gear casing, but a good rebuilder should be able to do it during a rebuild. If you decide to go this route let me know and I can recommend one to you that has done this conversion.
I have a '67 box in my '65. I believe it's a SMB-B which has the 16:1 ratio. The pitman arm is the same as any 65-66 and connects to the control valve just fine. That particular model is described as a manual steering application, but the ratio is the same as the power steering model.