4.6L for a v8 deisel ought to be plenty for any 1/2-ton.

It's not like you'll be towing 15,000 lb's with that vehicle.

Thats should make for one packed engine bay, though.

Of course, I have usually vouched for the easy way of doing things. Find a good diesel, cut it in half, then you have an I4 diesel for a lighter duty vehicle.

If this 6.4L is "all that", make a 3.2L I4 with twin turbos and stop there for now.