my 450 ford diesl heavy duty truck 2004 just died while driving why?

As much as I'd like to give you the magic "fix" for your truck there are to many things that can cause it to shut off. I work next to the diesel guy at a Ford dealer and have seen him have your model truck towed in for things a simple as the fuel filter cap left loose by an oil changer to the biggies like high pressure fuel pumps letting go. Not to be sarcastic but diesels require hands on professional help in most cases.

My 2008 F450 died in the winter, like yours while driving down the road. Code reader said low fuel rail pressure. This suggests needing a new high pressure fuel pump--very expensive. I did a lot of internet research and came up with this: Drain fuel from primary fuel filter to remove any water. Put dry tank in the fuel tank. Bleed air out of the lines. Fill tank with fuel. Walla--she runs. This past winter I kept tank full of fuel and had no problems.