OK 99' Dodge 360 gas with unspecified trans. so I will say an auto. with OD and factory gears in rear OK.
First things first. As stated earlier you do have a great engine with that 360 however it is gasoline and they can and will struggle in the hills unless you get a taller gearset which can effect your mileage and cause premature wear to your powertrain as well as your drivetrain. If you are running any big hills on a regular basis then everything is as it should be unless you wish to convert to diesel which will give you the torque required for running heavy through the hills.
Good luck