Slant 6 engine boss decoding

So it's definitely the original engine to the car. The numbers on the rear boss are C6223489. The last of the numbers match my vin. I guess the only way I'll know if it's forged or cast crank is pulling the oil pan, and measuring the connecting rod width. Cast are a little under an inch wide at the bottom, while forged are a little over an inch at the bottom.