Your money is going to be spent on the hydraulic parts, as converting to power steering isn't cheap. Even if you score a complete used setup from eBay for $200, most likely you'll need all new hoses, tie-rod ends, and a rebuild or reseal of the major components. If you want to purchase everything down to the last bolt, already rebuilt and ready to go, plan to write a check for around $1,500.
1 While not 100 percent necessary, we opted for the correct-tagged steering gearbox for a V-8 with power steering because our old gearbox was shot. The steering wheel and column will need to be removed for gearbox R&R. Remove the center cap or horn ring, then remove the retaining nut and steering wheel.
It would be great to hop in a time machine, go back to 1966, and purchase your Mustang exactly the way you want it. Of course, that's not possible, so owners often take small liberties during a restoration to add options and conveniences that didn't originally come with the car. Unless you have a rare Mustang or you're restoring your car to the letter of the buildsheet, adding power brakes, power steering, a console, Styled Steel wheels, and so on isn't such a bad thing. If the addition is done properly, using all the correct parts, can anyone really complain? We're talking safety and/or driving comforts here in the 21st century.
Our Project '66 hardtop is one of over several hundred thousand hardtops sold in the '65-'66 model years. There's nothing particularly rare about it and, with so many hardtops made, taking a few liberties here and there shouldn't be frowned upon. We are, after all, restoring the car and saving yet another Mustang from extinction, whether you like the modifications or not. It was decided right from the beginning the '66 would have power steering, just like the original '66 I owned 14 years ago.
The conversion to power steering is literally a bolt-on project. Approximately 90 percent of what you need to perform the conversion can be purchased new or rebuilt. The few things you might need to purchase used or find from a salvage facility include the power-steering-pump mounting bracket(s) and the hydraulic ram frame-mount bracket. Working with Metro Mustang for hard-to-find used parts, we located the correct power-steering-pump mounting bracket, the frame bracket for the ram, a pump core, and even the pulleys for the engine. We also found a good '66 power-steering center-link core at Metro Mustang, which was restored by Alamo Classic Mustang's Precision Products using a Stainless Steel Brakes Corporation control valve. We also used one of SSBC's new hydraulic slave cylinders, along with concours hoses from National Parts Depot. Last, we rang the Bramlett brothers at Mustangs Plus for the correct V-8 power-steering tie-rod ends, adjusting sleeves, and idler arm.
2 Once the wheel is off, remove the upper-column taper bearing. The column tube will not slide up with this in place. Use a small screwdriver to gently pry it free. | 
3 At the base of the column, unplug the wiring connectors for the turn signals and horn. Once these wires are free, remove the two nuts that retain the column tube clamp to the dash frame. | 
4 With the column-tube retaining bracket free, the column tube will slide straight up and off the gearbox's long steering shaft. |
5 Since we're getting rid of the steering box and all of the manual steering components at once, we left the major components assembled to each other and removed everything as a unit. The six-cylinder manual-steering idler arm (from the frame) and the passenger-side outer tie-rod end from the spindle are the first to be pulled. | 
6 On the driver side, simply disconnect the outer tie-rod end from the left spindle. | 
7 Three bolts attach the steering gearbox to the left front framerail. Once these bolts have been backed out sufficiently, the gearbox will be free, so watch the steering shaft to make sure it doesn't scratch the dashboard. |
8 Working carefully, slide the steering gearbox forward to clear the dash, and carefully fold the manual linkage in such a manner to allow removal of the complete system in one piece. If you have a V-8 in place and still plan to swap the gearbox, be prepared to jack up the engine and remove the driver's motor mount for room. | 
9 The manual linkage is shown here with the new/rebuilt V-8 power-steering linkage we temporarily assembled for comparison. The power-steering linkage mounts in the same locations, but it has provisions for hydraulic slave-cylinder mounting and the power-steering control valve. | 
10 The rebuilt V-8 power-steering gear box came to us refinished in a "natural" finish, so installation required nothing more than lining up the holes and reinstalling the three mounting bolts. At this time, you can reinstall the steering-column tube and steering wheel. |