Of course, it depends on how steep a mountain pass and how heavy your trailer (and how much wind resistance your trailer has, e.g. a travel trailer or enclosed car hauler), but in my experience it takes a STOUT V-8 to maintain 60 with say a 6000 lb trailer on a moderate interstate grade. A 454 or modern diesel can probably do it, but even a 350 won't be able to maintain 60 in most cases.
No way that is going to happen with anybody's 292.
Torque is only part of the equation - what you need is a certain amount of horsepower at the desired operating speed of the engine. You want to go up the hill quicker, it takes more horsepower. Period.
If you know the total vehicle weight and the gradiant of the highway, it is pretty easy to calculate the wheel horsepower needed to maintain any particular speed.
