Ford didn't stamp a vin on the engines, so there is no way to tell if it is the original, or a replacement. There is no "numbers matching" like a GM.
The casting number will tell if it the right vintage, but may not give the exact year, just the design year of the last revision. A 73 block could have C8TE, D1TZ, or D1OE. There should be a casting date code above the design code, first number for year, letter for month, more numbers for day. If there is a decal on the valve cover that will also have the month and day of assembly.