Maval (or Marval) has a manual rack that from the pictures looks pretty nice. Designed specifically for the Mustang. It's just under $900.00. I talked to the plant manager at one of the car shows the other day. He says it has 6.5" travel and 3.5 turns lock to lock. The travel means you would loose very little turning radius. Maybe 1', probably less.
If anyone is interested, I've got the information at home and can post a link.
I just ordered Randall's Rack. For the money, it's not worth my effort to duplicate. Very sharp guy, able to answer all the important questions very thoroughly, and authoritatively. There are ways to pick up the loss in steering, but it means changes to the chassis, ride height, spindle or all three. Just depends on how you set up your car.
YMMV,
Scott