horse power

more info would help

 

Alot of factors here. I rather have 600+ and keep a light foot.

 

In my experience every time I raise Horse power my fuel mileage would increase 1 or 2 tenthes if you keep you driving habits the same.

 

Better not get the cummins if you want decent GAS millage.

 

To paraphrase a member on this board "There is no such thing as Too Much Horsepower"

 

Seriously it depends where you'll run.
If you run the 70 in CO, the Donner, I-5 from the "Castiac Crawl" north as examples,
500 minimum with at least a 13 speed (18 is better) unless you like to watch the grass grow.

Run the "flats" on the east side of the divide, you could get by with a lower number of ponies and fewer gears.

 

If you tug pre-fabed beams or 60' pipes a W9 or a 379-389 would be better because they have (off the lot) the longer wheelbase. The 387's mostly have a 245" WB and you'd have to move the rails back for the fifth-wheel.
265" minimum unless you just run non-permitted loads.