Yeah the saginaw from C/S/K part number 20-6644 is a direct bolt in as long as you change the pressure hose too and its silent. It also makes it a lot easier to steer. Definitely one of the best mods I've done to my f150.
If I recall, my factory service manual has a procedure for putting vacuum to the reservoir while running and turning the wheels back and forth (off the ground!) to clear air bubbles that may cause the typical Ford whine. I've been meaning to do this as soon as I can find a rubber cork big enough to fit and hook my vacuum pump to.