OK, this is a very common upgrade, but, first, what engine do you have tucked in your vehicle? If you have to fabricate brackets for the pump and add a two belt crank pulley, it can be a bit of work and cost $800-$1000 depending on what you install.
Here's my attempt: http://www.members.shaw.ca/pavelb/steering.html
Doug, if you don't want to reinvent the wheel, but make your life easy, contact Willys America. They sell a bracket that welds in place to mount the new box. Any older chevy box will work if it was bolted to the inside of the frame on that car. Pickups, camaros, monte carlos...
They will tell you and sell you what you need to do this, minus the actual box and pump stuff. Any other vendor for Willys stuff will be able to as well. I just like putting in a plug for WA.
Contact Hermtheoverdriveguy! He just completed the final touches on a wagon conversion kit, I have been hounding him for months and it is now ready to go. I just need to be ready for the parts before I can place my order, but he has the mounting kit, pitman arm and tie rods all set up for use with a Ford Power steering gear box and pump.