440 duster. Need engine build advice

turn the motor upside down on the engine stand. pull the pan off and have a look see. a cast crank has sharp edges on the counter weights. also it will have 440 cast on it on the first counter weight. if the rods and piston were balance they in all probability were balance to the stock rod and piston weight. check the bottoms of the pistons to see if any holes or milling was done when the pan is off. if every thing looks good go to "440 source" and purchase a cast crank balancer and a cast crank flex plate.