The bolt pattern for the 1995 GMC Sierra is 6x5.5. This means that the wheels have six lug nuts that are spaced 5.5 inches apart. The 17-inch wheels that you are considering have the same bolt pattern, so they will fit your truck.
The only other thing you need to consider is the offset of the wheels. The offset is the distance from the mounting surface of the wheel to the centerline of the wheel. If the offset is too high, the wheels will stick out too far from the fenders and may rub against the wheel wells. If the offset is too low, the wheels will be tucked in too far and may not clear the brake calipers.
The best way to determine if the wheels will fit your truck is to take them to a tire shop and have them test fit them.
