Ford used the "sequence number" on the block....which is the last 6 digits of the VIN number of the car.
Different production lines used different numbers.... All Cougars started with 500000, Torinos as noted with 100000 Mustangs may have been same as Torinos, or simply 000000, I can't recall.....
But as George noted, first digit is typically the production year ie 3=1973. Not the date the block was cast. That would be the casting date!
What no one seems to have done much work on, was tracking casting dates to Pantera assembly/sales/production dates.... Would be quite the task!
If DeT got engines from the spare parts line they could have older dates....if they came from the engine plant directly, they should be fairly close to the production of the car....
SOOOO, your production dates on the block could vary....and to say what is correct for your particular car, knowing DeT's production line crazys...is really tough.
One really shouldn't be concerned at all with the VIN number stamped into the back.......
What tells you the most about your engine, is the casting number, the date code, and the dimensions of the cylinders.
If any one needs help with the numbers, drop me a line....but these are well published and can be found in the "How to Rebuild Your 351C" book also. I have the Ford Master Parts Catalog that the dealership used. Up thru 1972, last printing 1975.
Keep in mind that many parts on your engine have date codes that should be fairly close together, just like glass dates on the body!
Block, heads, intake, carb, distributor, harmonic balancer, water pump, fuel pump, flywheel, temp sender (Ford version) to name most of them, all have date codes!!!!
Now, if you are already worrying about your block.....this should have you in cold sweats!!!
