Maybe, maybe not. You have not stated what gear ratios are in the truck, type of terrain driven in, what engine, and what type of carburetor is on it.
If the truck has a 454 with a Holley then it’s doing very well fuel-milage wise.
Assuming the driving habits are not aggressive, the ignition timing is not a mile off, etc. then the truck should do much better on fuel economy than it is.