4" for the shackle reversal, must build (fab) up new front spring hanger mounts to retain proper geometry for steering axle. Can be expensive, the ORU kit from the states is close to $1000 CDN.
Is very safe and makes for a smooth ride in trucks with leaf springs up front!
Only one problem, you have a coil sprung front suspension, you must be talking about a shackle flip for the rear leaf springs. You will need the front spring hangers from the rear suspension of a Ford equipped with 3" wide springs. I took mine from a 74 F250 2WD Camper Special. Remove the rear spring hangers from your rear suspension, flip the shackle above the spring, and start drilling holes and aligning everything. I am sure a search on the subject on this BB and Pirate4x4's BB would net you additional information.
I spent about $100 in nuts and bolts to replace all the hardware in the back of the truck!