P/S fluid smells burnt, pump is squealing

I would flush out the old fluid from the system and replace with fresh fluid and maybe an additive that would take care of any leaks. It's worth a try before having to replace any parts.

As for flushing it, I don't know.

As for converting, you certainly do not have to replace the steering box. If you have the power box then you'll have to use some muscle in parking lots, but plenty of people preferred the power box without power as a more responsive (fewer turns) steering option. Most mustang parts houses sell an adapter that replaces the control valve.

Flushing the system is pretty simple. Disconnect the return hose at the P/S pump and put it in an empty bottle or jug (anti-freeze or washer solvent bottles work well). Top off the P/S resevoir with fluid. Have someone start the vehicle while you continue to add fresh fluid to the resevoir. This will push out all of the old fluid in the slave cylinder as well as the lines. When the fluid is coming out clean, put the hose back on the pump and top it off. A couple of other tips. If your power steering hoses are swelled up or distorted, they will need to be replaced. After you close the system back up,you should turn the steering wheel back and forth with the engine running to get out any air that may be trapped. Good luck.

Hey Sad but True, ever get your P/S problem fixed?