I was gonna ask about the upper and lower A-Arm assemblies for 66-67 Farlanes interchanging with the Mustangs, but Dan beat me to it.

Next question: Is the Power steering center link from a 67 Mustang the same as a 66-67 Fairlane? I know the rams and control valves are the same. I just picked up a 66 GTA-S-Code car, but the PS had been removed and I want to put it back.

Also, what about the PS gear box from a 67-68 Mustang? Will it fit on the Fairlane?

I believe the drag link is different between the 2nd gen Mustangs and Fairlane...but that's just my recollection and should come with a proviso that you need to find someone with a master parts catalog to confirm.

The steering box answer is: it depends. First, go to this site to understand the differences: http://www.stangerssite.com/steeringboxtagdecoder.html

A '66 Fairlane would have a long shaft box in most cases. The change to the short shaft occurred in '67 for both Mustang and Fairlane. If you have a short-shaft box, then there is interchangeability. Long-shaft and it's not so easy.