the limits of diesel

I know they advertise 25 MPG for the 1500 with the base V6, but did not say the configuration of transmission and rear end ratio. A basic, extremely light duty truck.

It is thus far about the transmissions. It seems with programers and tuners, it's alwasys the transmission that goes 1st. With a tune, intake, exhausts, electric fan, my duramax was over 1,000 torque at the wheels and 489hp at the wheels.
Many diesels, ford, chevy, dodge, can take 50-75hp and a couple hundred more, but it will cost you a transmission rebuild.

It's a cat an mouse game right now.
Used to be a good toy hauler was 18,000 lbs. Now they can be as heavy as 21,000 from what I've seen. Then TC with 4 slides push 6,000 lbs also. I don't think the old wood ones in ol' days were near that. I personally like the horse power wars.
But, I think at 21,000 lbs capacity, 850tq, etc, I'd wish they would focus on the MPG part a lot more!

Looks like Ford is going to upgrade the current 6.7 to around 500HP and close to 900lbs of torque for the 2015 model. Ford is putting in a new turbo and a larger toque converter for the tranny.

Not 100% sure about this because I was only half watching/listening to the football game when the Doge/RAM commercial came on. I thought they were talking about RAM series, "best in series" of trucks in general. So I thought they meant the Cummins got the 850 lbs of torque and maybe it was the 1500 series that got 25 mpg. I know that's what it says on the RAM website.

I think that 25mpg must be for the half ton diesel. I know people who get 1000 foot pounds but most of them run manual transmissions. The few with automatics have very beefed up systems.

I think it just depends on how anemic you want the power to be. I think it is reasonable to think that a diesel truck could have similar gains over a gas engine similar to a diesel vs gas car.

I don't think their's really been much effort on mileage for diesel pickups. The same is the case for larger gas pickups although smaller trucks are starting to have a mileage war.

1000 ft-lb is not out of the realm especially with the Cummins. But until transmission technology catches up your not likely to see it.

I am curious (not disagreeing with you) - Where did you see a specification of 25 mpg? I have never see a light truck tested for mileage.

(personally I am thrilled when I can get 16 MPG unloaded)

As far as your original question - how much performance can you get in a light truck? How big is your engine compartment and how much weight can your front axle hold?