Anyone help with these stamped block numbers? 3R156103? The 6 could be an 8. Thanks

 

What block casting number is this? In any case, you're missing one digit. The VIN derivative is a nine character stamp. I suspect your block is really stamped 33R156103.

3 = Oldsmobile Division
3 = 1973 model year
R = Arlington, TX assembly plant
156103 = last six digits of the VIN from the car this block was originally installed in

 

Your right Joe. It dose start with 33. Someone wanted to know if I would be interested in buying a block he has. Only numbers he sent me. Not interested. Just curious to what it was.
Already have one to many laying around I really don't need.

Thanks