Chevrolet wheel bolt patterns are available on the Web at wheelhelp.com. The site includes wheel bolt patterns for Chevy models built between 1955 and the present. The chart also applies to General Motors vehicles.
Another site with Chevrolet/GM charts is wheellugpattern.com. It includes models made between 1955 to the present.
You can use a bolt pattern gauge, which is available at auto parts stores. Alternatively, with the wheel off, use a measuring tape to measure from the center of one bolt or stud to the center of the bolt opposite it. That measurement following the number of bolts is your pattern.