Ford Repair: Block casting numbers, ford division, block numbers

Question
I have a 1966 ranchero , the original motor is gone and it has what appears to be a 74 302 (D4DE 6015 Z)  from a Falcon donor in it now.My question is ,what does the Z stand for and , what do the other numbers and letters that are cast into the block stand for that are right below the block numbers ? ( 7C15 , or possibly 7C18 ) Thanks , Bill  

Answer
Bill-

  The "Z" is commonly found on what are called "replacement parts" even though few of the items are replacements.  In this case, "Z" simply stands for "Ford Division".  As for the second code, it's the date code.  Yes, Ford is nice enough to tell you what day exactly that the block was made.  In this case, March 15th (or 18th), 1977.  The "7" is the year, the "C" is the month (Jan. = A, Feb. = B, etc.) and the last 2 digits are the day.  It's not uncommon for a block to be stamped with codes that seemingly contradict each other.  It just means that the original design was from '74 and they didn't update it before casting your block.  I've also found that, despite what the model code says, many blocks find their way into cars that have nothing to do with the original model indicated by the first code.  Really, all you need to know is that you've got a '77 302.  Hope this helps.

Steve