small block differences. someone want to fill me in please?

My '72 duster 340 also has the forged crank. When I bought this car in june of '76, the engine had never been out of the car, so I know it was factory installed as well. And it has the 727 auto. I would say that Mother Mopar was using up the forged crank stocks until they ran out, being that they were switching over to the cast units for the '73 model. I passed up on a new '73 Duster 340 auto in 1973 at the dealers for $3300.00, because of the cast crank. Which I later learned wasn't really an issue because the cast cranks are more than strong enough for serious performance duty. Many 10 sec. cars have them. Unless I have a clutch car with 'big' tires and steep gears, the cast crank is fine. Good luck,
Terry.