Look at the crank from the front end. You will see a "parting line" that runs up the front of the crankpin. If this line is 1/16-1/8" wide. The crank is cast. If the line is 3/8" or wider, the crank is forged steel.
Cast cranks last hundreds of thousands of miles in production engines. Unless you are building a 600 horse engine. Cast is fine.