With great respect for AndyF other than the caliper nothing else there will work(I don't think). Been awhile since I messed with these brain cells but for sure the Imperial used larger wheel bearings than the C bodies as well as different ball joints and if that was not enough I don't think you can get a Mopar Al Wilwood hub with enough meat on it to drill a 5x5 pattern.

Now, if you don't mind running 4.5x5 in the front and 5x5 in the rear you might be able to fake it out and replace everything between the upper and lower arms in the front (might have to change the upper arm??) and then you would have "normal" C body brakes available to you. You would want to use late '72-'73 C body stuff, the non-Budd brakes. But then you are back with just factory brakes and still going to have to work hard to put something more/better/bigger together. Add a rear axle shaft and rear brakes swap out to the list if you want everything at 4.5x5.

Check out Imperialclub.com and here http://www.imperialclub.com/Repair/Brakes/mike.htm for a Toyoda Supra brake rotor ideas. Still not big brakes but you might get some ideas.