First a disclaimer: I represent the gnat that buzzes arournd the big stuff so I don't know much about big blocks, but you need to get your part numbers correct. If you're referring to a Ford part number, the first character is a letter, and that letter represents a decade; as in B=1950, C=1960, D=1970. The second character is numeric; a number as in 1, 2, 3 etc, and that is the year. The third character is the product line; F=Ford, Z=Mustang, V=Lincoln. The fourth is the part's family, F=fuel, W=rear axle, E=engine. Then we get into the part's basic part number, in your case the part number should be 6015, not 8015. The last character (or two) is a variation in design. So what you are looking at is p/n D1VE-6015-AA, an engine casting part number. What that means is you are looking at a Lincon block, originally designed in 1971. The heads are p/n D0VE-(xxxx)-C, (sorry, the casting part number is not readily avaiable).
Off hand I would say you have a Lincoln Continental block, not Mustang.