I had the same problem with my 1999 F450,it is easy to get the wrong calipers,bleeders have to be on top to bleed properly,invest in a $50 vacuum pump as these calipers are huge and pumping the brakes too soon just adds more problems,was able to remove most of the air with the pump and a couple of brake pedal pumps with a helper got rid of the rest.Had a bit of an issue with low pedal when first starting truck but a few hard stops and the pedal was better than before.When bleeding calipers,it is easy to know if the air is out as they will start working as your helper is applying pressure while you are working the bleeder.