Back in the 1970s, I had the Cyclone headers on my 66 Fairlane GTA 390, and they fit fine, but since this was going to be more of a drag car than a street cruiser, I had already converted the car to manual steering, so I can`t offer any input into how they would work with power steering, nor with clutch linkage, as my car had a C6.
As for power steering in general, on shock tower cars, I have installed on several of my 70 Mustangs, both with 351 C 4 V, and 428 Cobra Jets, with automatic and 4 speed transmissions, and in each instance, a power steering "drop bracket" was required to clear the PS cylinder. The typical drop bracket, supplied by the header manufacturers present at least 2 common problems, first, the rather flimsy steel construction tends to allow the drop bracket to flex, which reduces the already marginal road feel of that style of power steering, compared to the shorter, and much more rigid cast iron factory cylinder bracket. The can also tear the factory "Riv Nuts" out of the frame rails , that the bracket is mounted to , in the bottom of the frame rails. This can cause the shaft of the cylinder to get bent, as well as making the steering very stiff and sloppy, as the steering cylinder is no longer actually solidly connected to the frame. I have also had the drop bracket, which is made from 2 pieces of steel welded together, break at the weld. In each case, I ended up welding the bracket solidly to the frame rail, and gusseting the 2 sections, to reduce the flexing. It would be nice if somebody offered a much more robust, and stiffer drop bracket . although the Riv Nut mounting situation would still need to be addressed.
Concerning the Hooker 6113 headers for Fairlane/Comets, the 2 front tubes on the drivers side, hang down very low, as they run below the lower control arms, so ground clearance is a very real concern, even at stock ride height. Especially on a street car that encounters speed bumps, dips in the road, or steep on/off ramps. Frankly, for anything other than a race car, I I am a big fan of the FPA headers, although I don`t know how they work with power steering, or the factory clutch linkage on a Comet/Fairlane.