The E250 steering box is the same as the Bronco. What is different is the PS pump. The E250's use a Saginaw pump which is a lot better and stronger than a Ford pump. You will need the entire mounting bracket off a E250 with a serpentine belt system. It is basically the same bracket you have, with the exception of the mounting holes for the pump. If you get a junkyard donor system, I would suggest you get a rebuild kit for the pump. The rebuild is easy except for replacing the shaft bushing, you will need a hydraulic press for that. The reason I suggest a rebuild kit is that you don't know what the internal condition of a used pump is. Other options is getting someone else to rebuild it, get a re-manufactured pump, get a bran new one, (Parts store, ebay, etc. sell them).
If you need to replace your gear box, there are several on the market from a stock replacement to heavier ones. If you have slop in the steering wheel you may simply need to adjust the existing box.
I have done the conversion on a V-Belt system and can only comment on the serpentine system from what I have read by other people that have done it, but you will need the mounting bracket, a Saginaw pump, the pulley from the Saginaw pump, and the high pressure hose (get a new one), and one guy I read said he had to get a slightly longer belt because to Saginaw pulley was bigger than his old Ford pulley. I would also flush the system of the old fluid, I did that by capping off the pump low pressure connection and dumping fluid into a pan under the truck while running the engine and keeping the pump topped off, (
DO NOT let it run dry ). It helps to have someone to start and stop the engine while you do this, I am using transmission fluid in my system.
Good luck,
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