The D1 doesn't necessarily mean it came out of a 1971 model year vehicle. Ford changed casting codes when there was an engineering change. The date code should be right above the casting code and look something like 1A17 - the first number is the last digit of the year (so in this example, it would be 1971), the letter indicates the month (A=January, I is not used so J=September), and the final number is the day of the month.
The 6015 identifies it as an engine block, so really doesn't provide any additional information.
As for your block, it appears from the casting code to be a Mexican block. Quoting from
http://phystutor.tripod.com/stang/engines/small.html:
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR> Some 302 blocks cast in Mexico have thicker, 289 HP style bearing caps. These were supposedly made with a higher nickel content alloy. Folklore claims these to be beefier than other blocks. On my bathroom scale a 1970 dated Mexican block weighed within 1/2 a pound of a regular 1970 302 block. That must be some lean beef.
Identified by casting numbers C8AM-B, 75ZY-AA, D1ZM-AA, among others, these blocks may be spotted by the "Hecho En Mexico" cast in the lifter valley. An extra unmachined boss protruding from the front of the driver's side cylinder bank can be easily spotted at the junkyard. <HR></BLOCKQUOTE>
As for specifically what kind (model) of vehicle it came out of, I couldn't say...
