JH,
The problem as I see it is that all the PS boxes are big and cross steer. They get in the way unless they are front mount with a lot of U joints and stuff. For a drag link type setup, some of the roadster guys that want cowl steering are going with a Dodge 70's type box that can be mounted on it's side. It's aluminum too. LOL.
I've seen a power steering rack that was rear mounted, but was mounted to the axle with a splined joint for suspension purposes. The alignment and the ackerman worked out, but it looked too much like it came from your area (Mickey Mouse)LOL. Just a couple of ideas for you to ponder.
Regards
Dennis