Might do to well to consider that one "accelerates" by shifting gears. I know that sounds obvious, but there is no way to wind out a Class 8 diesel.
Detroit 60's are okay, they have their problems. Their advantage is light weight and pretty good mileage when correctly spec'd. They make some nice noises and have a good feel when accelerating.
Spec'ng big trucks is, literally, a full-time job.
Try choosing, from just one of a dozen lines by Rockwell, the seventy-three variations available.
Or rears.
Cummins and Cat are likely still the HP leaders (600 HP and 2100 ft/lbs) last I looked a year or so ago when still driving.
Most rigs running down the road are more like 425 HP and 1800 ft/lbs.
Company trucks are lesser-powered and geared, and independents more likely to be running 13-speeds and big power. Knowing how to use it is the key.
1/2 mpg can make or break an operation in some instances.
As to torque, when I was driving flatbed and was delivering some big-diameter cast-iron pipe to a worksite, being able to shift to first (rarely used granny gear), never touch the fuel pedal and make it around a fenced turn on an incline from a dead stop at 78k gross was always impressive. Nothing in the truck changes: the A/C still blows ice-cold, the temps stay within range, etc.
But that particular Cat motor weighed 3,465-lbs and the Super 10 trans weighed over 800.
By itself, no trailer attached, the usual tractor weighs 18k.
Read Bruce Mallinsons articles:
http://www.dieselinjection.net/