I have a 1966 7 Liter Galaxie with 428 and power steering. With the help of my mechanic buddy, I added the '65-'67 427 cast iron headers quite a few years ago. They do fit. A couple thoughts I'll throw out there - when we did it the car already had the power steering installed, is it possible you need to take a header off first to install the power steering gear box? Where exactly are you seeing interference? We also installed NOS rubber motor mounts at the time of the header install to be sure sagging motor mounts wouldn't cause an issue - are your mounts in good shape? I looked in the Ford parts book, it looks like Ford used 2 different power steering gear boxes in the '65 to '68 period - a Saginaw box and a Ford box. They can be I.D.'d by the code on the tag attached. I don't know how they differ, but it's possible one works with the cast headers and one doesn't? Unfortunately my car is stored away from home so I can't immediately take a look at anything.