[capteddie]

Here's what I found....

The Service Part Number (D4DE 6015 BA in this case) will not tell you when the block was cast. It only tells you what decade and year the part was originally relased for service (which is not necessarily the same year it was cast, although it may be the same), what model line it was originally released for, what engineering department was responsible for it's release, what the part is, and what design level (how many minor changes it has gone through) of the part is.

D = Decade of release (1970s)
4 = Year of release (1974)
D = Model line (Falcon 1960-69, Maverick 1970-74, Granada 1975-82, LTD 1983-up)
E = Engineering department (Engine)
6015 = Engine block
BA = Design level (starts with A then B, C, D etc, then AA, AB, etc)

There is a Date Code on the block. It's in the same area as the Service Part Number. The Date Code will tell you the exact day the block was cast. It is arranged in a YMD(D) fashion and will look something like 6D23 (which would be April 23, 19x6).