The 1982 Chevrolet K5 Blazer with a 5.0L engine typically has a radiator capacity of
around 18-20 quarts. However, this is an approximation. The exact amount can vary slightly depending on the specific vehicle configuration and whether it has an auxiliary transmission cooler integrated into the radiator.
To be certain, consult your owner's manual. That will give you the most accurate information for your specific vehicle.