383 engine #'s

it should have a date code cast into the side of the block left side above the 2468130-8- and perhaps a clock with a pointer and around (below generally) there with an arrow pointing to D for day or N for night shifts that will be when the block was cast. Generally it would have been used +/- 3 to 6 months later.

On the front left side of the block under where the head bolts on there should be more numbers (PT383xxxxxxxx) there and they will be engine assembly specific. the pan rail number are part of a VIN from the vehicle it was used in. So with a 383 1468130 block 1959 -71 the vin on it is 68-71 that's when they started doing that.