I got 8.5 mpg's towing in the pic below with my 8.1
But I get at what you're trying to portray here.
This would go in Scott's crew cab which he uses for not only wheeling, but towing too. I don't think he tows crazy heavy with it, I'm pretty sure he tows his hardside up to the mountains with it, so looking at towing mileage I don't think is the main concern, I could be wrong though
I like the 8100, it's a good engine, and kind of a hybrid engine with a stroker crank and stock spread port style heads for better efficiency. But if I was building one I would stick with a Mark IV or Gen VI for cost reasons.
And nice rig, cool setup, looks like you could get into all sorts of fun with that.
I am talking 9.5 MPG with th huge 32 ft enclosed on the freeway, if I slow down a bit on a highway I can get 10-11 MPG. That camper is probably similar, its like towing a brick wall down the road, the wind resistance seems to matter more than the weight. (trailer is about 10k lbs loaded)
If I tow just the truck on my open trailer I get 11-12 MPG depending if its a highway or a freeway if you know what I mean. (trailer is about 7k lbs loaded)
I guess my point is, the diesel is nice and torquey, and almost necessary if you start towing over ~12k lbs, but it's not going to pay for itself in fuel savings these days with the DI gas coming so far and the diesels being some crazy $8k upgrade or something. And now they have a 6.6L DI gas motor coming out for the HD trucks with more torque. Still not 900 lb-ft to fly up a mountain pass but definitely a good engine for the money I bet.
I just took the dog for a walk and I was thinking about this. I think if I'm honest with myself, I probably have a $3000 spending limit to hop up a 454.
I agree with Kay, aluminum heads and a hydraulic roller cam, you'll need new pushrods (1 piece) and if you have the money a set of steel roller rockers and run it. I think you could still achieve ~500 hp. Maybe you can save some money by buying one of
@AJs72K5 old roller cams.
With respect to heat/engine temps, is there any concern about using aluminum heads in a moderate performance towing application? Ideally, the cooling system temp should be fine but if towing in mountains or long uphill climbs would the temp get higher (but not overheating) than you'd want?
Not in my opinion, I agree with Beags and Kay, aluminum gets softer at lower temps than iron so it may warp a little easier if it does get
way overheated, but it also conducts heat better to the coolant than iron so it also should be less likely to overheat assuming your cooling system is good. But in reality the weight will matter more than anything else. It would not worry me one bit to use aluminum heads on his rig.[/QUOTE]
Kinda like the old saying, "if you have to ask, you can't afford it". 
