* Check the sticker on the driver's side doorjamb: This sticker lists the recommended tire size and inflation pressure for your specific vehicle. This is the most reliable source.
* Look at the sidewall of your existing tires: The size is printed on the sidewall of each tire.
* Consult your owner's manual: The owner's manual should specify the recommended tire sizes.
Common sizes for a 1996 Silverado 1500 include options like LT235/85R16, LT245/75R16, and P235/75R15, but again, this is not exhaustive. You *must* check your vehicle's documentation or the tires themselves to know for sure.