4.5L? That’s still larger than *should* be necessary for adequate performance in a light-duty pickup. I’ve seen 20-ton straight trucks that were hauled around by an engine no bigger than that.
The Europeans and Japanese have smaller turbodiesels, but the 4.5 V8 is that size for low end torque and refinement - they’re thinking about putting the same engine in cars while they’re at it and they want to make sure diesel doesn’t have a performance penalty for their products (like it does over in Europe).