Good choice of the 4.10 gears. My Chevy V-8 had maximum torque (which is what is important when towing a load) at 4000 RPMs'. Check the manual for your specific vehicle as GM produced engines with different power bands for different vehicles with this engine. Older versions of this engine would produce peak torque at 2800 and 3400 RPMs and were designed for truck use.
It may be disconcerting to have lots of cars stacking up behind you and sometimes there is the option of using a pullout on the highway to let them pass. In some states by law if there are a certain number of cars behind you there is an obligation to pull over though I very seldom see anyone being courteous and actually doing this in the USA.
I try to find routes with as little highway traffic as possible and this helps all the way around.