Mautemps,
The 'D' is the decade. B = 50s, C = 60s, D = 70s, E = 80s, F = 90s
The '2' is the year of the decade. Thus, D2 = 1972
The 'O' is the car line the part was originally designed for. In this case, O = Fairlane/Torino
The last 'E' doesn't really mean that much in this case because it is a casting number or sometimes you'll find this kind of designation stamped on a part (stamping number) Casting numbers and stamping numbers are just identifying marks for assembly plant use. The casting number or stamping number may or may not be the actual part number.
The 8B19 on the line below the casting number is the date the part was cast. in this case, the first digit is the year. 8 being 1978 or 1988 or 1998 in this case. Since the casting was 'D2' or 1972, you know the block was cast after that.
The 'B' is the month. A = January, B = February and so forth. The letter 'I' is not used so 'J' = Sept and go on from there.
the '19' is the day of the month.
Your date code therefore is February 19 of 1978,(or 1988 or 1998)