A truck like that is geared more like a dump truck. Local work and sometimes traveling on highways.
It is geared low like that so that it is easier to pull heavier loads and be able to crawl off road.
A good usage for a truck like that would be pulling a low bed or going into landfills.
It is a different spec than an over the road truck.
Tall 24.5s would help a little and the 18 with .73 od would help also.
You may already have both.