Your bus will likely have both specs from the chassis manufacturer and the coach company.
There is a lot of useful information on these labels:
The month and year of manufure and the chassis manufacturer might be listed.
[GVWR] - Gross Vehicle Weight Rating:
This is the total weight of the vehicle, including driver, passengers, and the load it is carrying. This figure is given in pounds.
[GAWR] - Gross Axel Weight Rating:
You should have a total listed for both the front and rear axel. This is the total permissible weight allowed on the axe, and is listed in pounds.
Suitable Tire and Rim Choice:
On a new bus it may list the tire and rim size for the front and rear along with the proper tire inflation pressures.
Cold Inflation Pressure:
Check your tire pressure when tires are "cold" and have not been driven more than one mile.
Other information such as vehicle type, color, identification number, vehicle model, etc may also be listed.
The chassis specification label will tell you more information specific to the truck that your body has been placed upon.
It will list the manufucturer and model along with:
[WB] Wheel Base:
This is the distance between the centers of the front and rear wheels and is measured in inches. Measuring and comparing the wheelbase on both sides of a vehicle can identify rear axle misalignment or front wheel setback.
Certified Net Horse Power:
The horse power measurement taken at the driven wheels of a vehicle on what's called a dynamometer. The engine speed at which this amount of power is acheived is also listed.
Certified Gross Horse Power:
The horse power measurement of engine output, taken at the flywheel, without the engine installed in a vehicle. The engine speed at which this amount of power is acheived is also listed.
[Max GVW] Maximum Gross Vehicle Weight:
The maximum permissible weight of the unit, including the UVW plus all fluids, cargo, optional equipment and accessories. For safety and product performance, do not exceed the GVWR.
[CW] Curb Weight:
The weight of the unit without factory or dealer installed options, plus allowance for the weight of full fuel capacity. The "payload capacity" for all other fluids, cargo, occupants, optional equipment and accessories can be determined by subtracting the CW from the GVWR.
[GCWR] Gross Combined Weight Rating:
The maximum total weight of the loaded unit, plus a tow vehicle. This includes the weight of both the unit and tow vehicle, fuel for each, all other fluids, cargo, occupants, optional equipment and accessories.
Figures such as base weight and carrying capacity may also be listed.