2001 E-450 front calipers siezed-what now?

^^^ Correct. Hose develops a "check valve." Worse with Disk Brakes than Drum Brakes. Drum has return springs to help get the fluid back out of the wheel cylinders. Disk only releases the pressure of the caliper pistons. I've seen the relief port in a disk brake master cylinder "heal up" with corrosion, there's so little flow back to the master. Personally, I don't worry much about the rear hoses if the vehicle is four-wheel disk brakes. All those do is form a flexible connection so the caliper can release and the pads can wear. They don't rise/fall with the suspension like the fronts do, and of course they don't steer. I'll replace the rear hose between chassis and axle, but usually not the two between each end of the hard lines on the axle and the calipers.