I agree that swapping in a used motor is the most practical solution given how much the truck cost and its use. It's a shame though - kind of surprising. 300's can go hundreds of thousands of miles, it's surprising to me it has a dead cylinder - what specifically constitutes dead? What lead to the conclusion? If it's something like a burnt valve, then maybe a valve job is a better solution. If it threw a rod then that's a different story.