I have a 350 4 bolt block and was wondering if chevy ever put forged cranks in these motors. If so how would i know?

 

Yes.

Look at it.

A forged carnk has a real wide parting line, like ½" or so. A cast crank has a real thin narrow parting line, like 1/8". Also, the sound is different, if you tap it with something metal.... a little like the difference between a silver quarter and a cheapium one.

 

Look at the casting number and see what year it was made. Mortec will tell you that. Recent blocks probably dont have forged cranks. If it's out of the car, just pull the pan and have a look. Cast cranks will likely have a fair amount of casting flash with a thin, sharp parting line; and like RB said, a forged crank will have a wide one.
matt