I'd stand on it if necessary. I used to tow a TT with a '96 Dodge 1500. It wasn't uncommon to have the pedal on the floor going up a mountain. The old 360 did great, just a little slow.
Modern engines make HP at high RPMs; they also have things like rev limiters and torque management to keep you from breaking things. You should be able to stand on the gas up a grade and not worry about anything.
However, I'd find out what RPM your engine produces it's peak torque rating. That's where I'd try to keep it if possible when going up a steep grade.